Start by slicing the cucumbers with a knife into thin slices. You can use a mandolin if you desire. Chop up the onion into thin half-moons as well. Slicing the veggies as thinly as possible is very important because that will allow them to absorb the dressing and seasonings easily. Combine cucumbers and onion in a medium-sized bowl.
Season with salt, sugar, and freshly ground black pepper. Omit the pepper if you don't like spicy flavors.
In a small jar mix apple cider vinegar, olive oil, and water. Pour the mixture over cucumbers and onion. Toss until veggies are evenly coated with the vinaigrette and well combined.
In the end, sprinkle with toasted sesame seeds. This step is optional but it gives the salad a nice earthy and nutty finish. If you want to learn how to toast sesame seeds at home check out my post for Homemade Tahini Recipe. The first step explains the process. After that, I recommend you refrigerate your cucumber salad for at least 30minutes or until serving (the longer they marinate in the dressing, the better the flavor).
Before serving, stir again to evenly mix the vinegar dressing. Enjoy it as a healthy snack on its own or serve it alongside your lunch or dinner. Store covered and refrigerated for up to 2 days.
Notes
Use any cucumbers you have at home: Persian cucumbers, Kirby cucumbers, or any garden cucumbers. I didn't peel them but if yours have very thick or bitter skin you should remove it.
You can use any type of onion here: red onion, yellow onion, white onion or scallion.
If you like your salad to have an intensely sour taste, use white vinegar or substitute the apple cider vinegar with balsamic vinegar, red wine vinegar, or rice vinegar.
You can make an oil-free version of this easy cucumber salad by omitting the olive oil.