If you want, you can peel the cucumber. Otherwise, just clean it with a brush and then finely slice it. You can either do this by using a simple kitchen knife or a vegetable mandolin. With a mandolin, you can achieve especially thin and even slices.
Place the cucumber slices in a colander and sprinkle with approximately 2 teaspoons of salt. This will draw out the excess water so you can avoid your salad from becoming soggy. Leave the cucumber to drain for around 30 minutes to an hour.
While the cucumbers drain, prepare the dressing by peeling and finely chopping the onion (this step is optional, but adds a nice crunch to the salad). In a jar, whisk together the vinegar, oil, chopped onion, and sugar until well combined.
Once the cucumbers have drained, pour the dressing over them, add the fresh dill, and toss everything together. Season with salt and pepper to taste, then serve chilled.
