Slice the cucumber thin. I do this quickly using my mandoline (I cut it into 2mm slices). Add the cucumber slices to a colander. Sprinkle them with the salt and toss with your hands to evenly distribute it. Place the colander in the sink or on a plate to catch the water that will be released. Let it sit for about 30 minutes.
Meanwhile, make the dressing by adding the sour cream, vinegar, sugar, dill, and pepper to a medium bowl and stirring together until smooth. Taste & adjust if required. Refrigerate the dressing until needed.
Chop the onion and add it to a salad bowl.
Once the cucumber is ready, give it a quick rinse in cold water and then thoroughly dry it using paper towel. Add it to the salad bowl, pour the dressing over, and toss. It should still be salty enough, but if not, add more salt prior to serving. I recommend eating this salad within a short time of making it because it does go more watery the longer you leave it, but you can chill it for 15 minutes or so prior to serving if you wish.
Notes
If you prefer less sweetness, use half the suggested sugar amount and then add more if needed.
Serves 4 as an appetizer or side salad. Recipe is easily doubled.
Nutritional information note: The salt is mostly rinsed off, so it's not included as part of the nutrition info calculation, but keep that in mind if you need to consider salt for health reasons (there will still be more than indicated).
This recipe is also on page 222 of the Salt & Lavender: Everyday Essentialscookbook.