Slice your cucumbers thin, about ⅛ inch if you can. A mandoline makes this faster, but a sharp knife works just fine.
Place the sliced cucumbers in a colander, sprinkle with a pinch of salt, toss to coat, and let them sit for 45 minutes to an hour. This draws out extra moisture and makes the salad creamier and more flavorful over time.
In a medium bowl, whisk together the sour cream, red wine vinegar, dill, garlic powder, salt, and sugar. Season with black pepper to taste.
Add the cucumbers and sliced onion to the dressing and toss to combine.
Transfer to a container and refrigerate for at least 1 hour before serving.