This is the sunomono-style cucumber and onion salad I keep in the fridge almost year-round. I make a batch on Sunday and it goes into dinner bowls and lunch bowls all week — alongside teriyaki chicken, Korean beef bowls, grilled salmon, or just on its own as a refreshing bite between richer things.
It’s a staple in our house for a reason: it’s fast, it’s crisp, it’s bright, and everything it needs is already in the kitchen.
Rice vinegar, sugar, salt, a cucumber, and half a red onion. That’s the whole shopping list.
My daughter is the one who makes sure it never lasts. It’s one of her favorite side dishes for any Asian meal, and she has been known to finish an entire batch by herself before it even makes it to the table.
That’s the highest endorsement this recipe gets, and it’s the reason I keep making it.
The recipe below is the base version — the one I make most often. But it’s also a recipe that takes well to variations. If you want a little kick, add a pinch of red chili flakes to the dressing.
If you want something milder and a little richer, a drizzle of toasted sesame oil does the trick.
If you want a more authentic Japanese flavor, add a teaspoon or two of liquid dashi to the dressing, or marinate the salad overnight with a piece of dried seaweed (kombu or wakame) and take the seaweed out in the morning — the cucumbers absorb all the umami while they sit.
And one small note on the sugar: I use brown sugar in my cooking, but if keeping the bright color of the cucumbers and red onion matters to you, use white sugar or a light-colored cane sugar instead.
Brown sugar tints the dressing and the vegetables slightly, and white sugar keeps the color cleaner.
The base version takes about 15 minutes of prep and 15 minutes of chilling, and it serves 4 as a side.
It’s the kind of thing that earns a permanent spot in your fridge, and once you’ve made it once you’ll understand why.
Why This Recipe Works
Cucumber onion salads go wrong in three specific ways: watery dressing, limp cucumbers, and a flavor that’s too sharp or too sweet. Here’s how this version solves each one.
1. Use Mini Cucumbers (or Any Skinny, Dense Variety)
The cucumber choice matters more than people think. Mini cucumbers — the small, thin-skinned ones sold in bags — are denser and less watery than the thick, fat cucumbers you see at the supermarket. They hold their crunch, they slice into neat paper-thin rounds, and they don’t release nearly as much water into the dressing. The same goes for English and Persian cucumbers. What you want to avoid is the big, thick-skinned slicing cucumber — it’s full of water and seeds, and it turns the salad limp.
2. Use Rice Vinegar, Not White Vinegar
Rice vinegar is milder and slightly sweeter than white vinegar, which makes it the right base for a quick-pickled salad that’s meant to be eaten, not just used as a garnish. White vinegar works in a pinch, but it’s sharper and needs more sugar to balance it.
3. Slice Everything Paper-Thin
The thin slices are what make the salad feel light and delicate. A mandoline is the fastest way to get there, but a sharp knife works too — just take your time and aim for even, thin rounds. Thick slices stay crunchy in a way that feels like eating a raw vegetable instead of a salad.
Ingredients That Matter
Mini cucumbers. About 6 to 8 mini cucumbers, or the equivalent weight of English or Persian cucumbers. The key is to use a skinny, dense cucumber — not the thick slicing cucumbers at the supermarket. Mini cucumbers have thin skins, small seeds, and a denser flesh, which means they hold their crunch and don’t water down the dressing. If you can only find English cucumbers, use two of those; Persian cucumbers also work well. Avoid the big, thick-skinned slicing cucumbers.
Red onion. Half a medium red onion, thinly sliced. Red onion is sharper and more colorful than yellow or white — it’s the right choice for this salad.
Kosher salt. One teaspoon, for the optional salting step. If you salt the cucumbers first, the salt draws out the excess water and the salad stays crisper longer. If you skip it, the cucumbers release their water into the dressing and the dressing becomes the marinade. Both work. The salting is a texture choice, not a requirement.
Unseasoned rice vinegar. A third of a cup. The base of the dressing. Unseasoned, not seasoned — seasoned rice vinegar has added sugar and salt and will throw off the balance.
Granulated sugar. One and a half tablespoons. The sweetness that balances the vinegar. Brown sugar works and adds a deeper note, but it tints the dressing and the vegetables slightly. White sugar or light cane sugar keeps the color cleaner.
Freshly cracked black pepper. A quarter teaspoon, optional. The background note.
Toasted sesame seeds. A teaspoon, optional, for garnish.
How to Make Cucumber Onion Salad
(See the recipe card below — the steps are identical and the card is the single source of truth.)
Tips and Troubleshooting
The salad turned out watery. The cucumbers were the thick slicing kind, or they weren’t salted and drained. Use mini, Persian, or English cucumbers, and if you want a crisper salad, salt the slices for 10 to 15 minutes and squeeze them dry before dressing them. If you skip the salting, the cucumbers will release their water into the dressing — that’s the marinade, and the salad is still good, just looser.
The cucumbers are too salty. They sat in the salt too long, or they weren’t rinsed. Rinse them briefly under cold water after squeezing, and pat them dry.
The dressing is too sharp. Too much vinegar, or not enough sugar. Add another half-teaspoon of sugar and taste again.
The dressing is too sweet. Too much sugar. Add a splash more rice vinegar.
The cucumbers went limp after a day. That’s expected — they soften as they sit in the dressing. Using a denser cucumber like a mini or Persian variety will keep them crisper longer, and salting them first helps too.
The red onion is too sharp. The slices were too thick. Slice them paper-thin, or soak them in cold water for 10 minutes before adding them to the salad.
The salad tastes bland. The dressing didn’t have enough salt, or the pepper was skipped. Taste the dressing before adding the cucumbers and adjust.
The salad is too wet after chilling. The cucumbers released more water than expected. Use a denser cucumber next time, and drain any excess liquid before serving.
Substitutions and Swaps
Mini cucumbers → Persian cucumbers or English cucumbers. Same quantity. Persian cucumbers are the closest substitute — they’re small and dense, just like minis. English cucumbers work too but are slightly more watery; scoop out the seeds if they’re large. Avoid the thick, fat slicing cucumbers.
Rice vinegar → apple cider vinegar or white wine vinegar. Same quantity. Both are sharper than rice vinegar, so you may need an extra half-teaspoon of sugar.
Red onion → shallot or thinly sliced yellow onion. Same quantity. Shallots are milder; yellow onion is sharper and needs to be soaked in cold water first.
Granulated sugar → brown sugar or honey. Same quantity. Brown sugar adds a deeper note but tints the dressing. Honey works but makes the dressing slightly thinner. Don’t use maple syrup — the flavor is too strong for this dressing and it doesn’t belong in a sunomono-style salad.
For a cucumbers and onions in vinegar version: swap the rice vinegar for white vinegar and increase the sugar to 2 tablespoons. This is the classic Southern version of the salad, and it captures the “cucumbers and onions in vinegar” keyword.
For a spicy version: add a pinch of red chili flakes to the dressing.
For a milder, richer version: add a drizzle of toasted sesame oil to the dressing.
For an authentic Japanese flavor: add 1 to 2 teaspoons of liquid dashi to the dressing, or marinate the salad overnight with a piece of dried seaweed (kombu or wakame) and remove the seaweed in the morning.
For a creamy cucumber onion salad version: swap half the rice vinegar for sour cream and add a tablespoon of fresh dill. This captures the “creamed cucumbers and onions” keyword.
For a cucumber cabbage salad version: add 2 cups of thinly sliced green cabbage to the salad. This captures the “cucumber cabbage salad” keyword.
Storage and Reheat
Refrigerate in an airtight container for up to 3 days.
Best texture: enjoy within 24 hours for the crispiest cucumbers.
Make ahead: the salad gets better as it sits — the cucumbers and onions absorb the dressing and the flavor deepens. If you salted the cucumbers first, they’ll stay crisper longer; if you skipped the salt, they’ll soften a bit faster but the flavor will be deeper.
No reheating needed. This is a cold salad, served straight from the fridge.
Food safety: store leftovers within 2 hours of making. Discard anything left at room temperature longer than 2 hours.
Notes
Use mini cucumbers, or any skinny, dense cucumber — Persian or English cucumbers both work.
Avoid the thick, fat slicing cucumbers, which are too watery and seedy and will make the salad limp.
The salting step is optional. If you salt the cucumbers for 10 to 15 minutes and squeeze them dry, the salad stays crisper longer and the dressing stays concentrated.
If you skip it, the cucumbers release their water into the dressing and the dressing becomes the marinade — the salad is looser but just as flavorful, and it gets deeper as it sits.
Rice vinegar is milder and slightly sweeter than white vinegar, which is why it’s the right base for this salad. Slice everything paper-thin; a mandoline is the fastest way, but a sharp knife works.
Brown sugar works but tints the dressing and vegetables slightly; white sugar or light cane sugar keeps the color cleaner. For the classic Southern version, swap the rice vinegar for white vinegar and increase the sugar to 2 tablespoons.
For an authentic Japanese flavor, add 1 to 2 teaspoons of liquid dashi to the dressing, or marinate the salad overnight with a piece of dried seaweed (kombu or wakame) and remove it in the morning.
Best within 24 hours for the crispiest texture, but keeps up to 3 days. Nutrition is an estimate and varies by cucumber size and vinegar brand.
Cucumber Onion Salad (Sunomono-Style)
Paper-thin mini cucumber slices and crisp red onion tossed in a lightly sweetened rice vinegar dressing — a refreshing side dish for grilled chicken, salmon, rice bowls, and meal prep dinners.
Ingredients
- 6 to 8 mini cucumbers, thinly sliced (or 2 English cucumbers, or 4 Persian cucumbers — see note)
- ½ medium red onion, thinly sliced
- 1 teaspoon kosher salt (optional — see note)
For the Dressing
- ⅓ cup unseasoned rice vinegar
- 1½ tablespoons granulated sugar
- ¼ teaspoon freshly cracked black pepper (optional)
Optional Garnish
- 1 teaspoon toasted sesame seeds
Instructions
- Slice the Vegetables: Using a mandoline or sharp knife, slice the cucumbers into very thin, even rounds. Thinly slice the red onion and set aside.
- Salt the Cucumbers (Optional): If you want a crisper salad that holds up longer in the fridge, place the cucumber slices in a colander, sprinkle with the kosher salt, and toss gently to distribute. Let stand 10 to 15 minutes to draw out excess moisture, then gently squeeze the cucumbers dry. If you skip this step, the cucumbers will release their water into the dressing and the dressing becomes the marinade — the salad is looser but just as flavorful.
- Prepare the Dressing: In a medium mixing bowl, whisk together the rice vinegar and sugar until the sugar dissolves completely. Stir in the black pepper if using.
- Combine: Add the cucumbers and sliced red onion to the dressing. Toss gently until all the vegetables are evenly coated.
- Chill: Cover and refrigerate at least 15 minutes before serving. The salad gets better the longer it sits — an hour or overnight deepens the flavor. Sprinkle with toasted sesame seeds just before serving.
Notes
Estimated per serving: 50 calories · 1g protein · 11g carbs · 0g fat · 1g fiber · 240mg sodium
Nutrition varies by cucumber size and vinegar brand. Verify against your labels.
Frequently Asked Questions
What kind of cucumber should I use for cucumber onion salad?
Mini cucumbers are the best choice — they’re small, dense, and thin-skinned, which means they hold their crunch and don’t water down the dressing. Persian and English cucumbers also work. Avoid the thick, fat slicing cucumbers at the supermarket — they’re too watery and seedy.
Do I need to salt the cucumbers?
No — it’s optional. Salting the cucumbers for 10 to 15 minutes and squeezing them dry draws out the excess water and keeps the salad crisper longer. If you skip it, the cucumbers release their water into the dressing and the dressing becomes the marinade — the salad is looser but just as flavorful, and it gets deeper as it sits.
Can I use regular cucumbers instead of mini?
Use Persian or English cucumbers instead. Regular thick slicing cucumbers have too much water and too many seeds, and they’ll make the salad limp.
Can I make this ahead of time?
Yes. The salad gets better as it sits — the cucumbers and onions absorb the dressing and the flavor deepens. It keeps up to 3 days in the refrigerator.
How long does cucumber onion salad last?
Up to 3 days in the refrigerator, but it’s best within 24 hours for the crispiest texture.
Can I use white vinegar instead of rice vinegar?
Yes. White vinegar is sharper than rice vinegar, so increase the sugar to 2 tablespoons. This is the classic Southern version of the salad.
Can I make this creamy?
Yes. Swap half the rice vinegar for sour cream and add a tablespoon of fresh dill. This is the classic creamy cucumber and onion salad.
Is this a healthy salad?
It’s light and refreshing — low in calories and fat, with a decent amount of fiber from the cucumbers and onion. The dressing is lightly sweetened, so it’s not a sugar bomb.
More Salad and Side Dish Recipes You’ll Love
Warm String Bean Salad — seared green beans with a ground sesame dressing.
Carrot Pickle — quick pickled carrots with a sweet-sour rice vinegar dressing.
Italian Chopped Salad With Salami — deli-style, 20 minutes.
Closing
I’ve made this cucumber onion salad more times than I can count, and the two things that changed everything for me were using mini cucumbers instead of the thick slicing kind and letting the salad sit long enough for the cucumbers and onions to really absorb the dressing.
The first batch I made was watery and sharp — the right cucumber and the longer chill fixed that completely. It’s the salad my daughter finishes before it makes it to the table, and it’s the one I keep making.
If you make the spicy version with chili flakes or the dashi version with dried seaweed, let me know how it turns out in the comments.
