Slice the cucumbers into rounds about one quarter inch thick and place them in a colander. Sprinkle with kosher salt, toss to coat, and let them drain over the sink for ten minutes. The salt draws out a surprising amount of water that would otherwise water down the dressing.

After ten minutes, spread the cucumber slices on a clean kitchen towel or a few layers of paper towels. Pat them firmly dry. This step is important. Wet cucumbers will turn your creamy dressing thin and soupy by the next day.

In a large mixing bowl, whisk together the sour cream, white vinegar, sugar, dried dill, garlic powder, onion powder, and black pepper until completely smooth. Taste it now. It should be tangy, slightly sweet, and herby. Adjust with a little more vinegar if you want more sharpness, or a pinch more sugar if it is too sharp.

Add the dried cucumber slices and the thinly sliced red onion if using. Fold everything together gently with a spatula or large spoon so every slice is well coated in the dressing. Try not to over-stir or the cucumbers can start to break down.

Transfer the salad to an airtight container. Smooth it into an even layer so the dressing covers as much of the cucumber surface as possible. Seal and refrigerate for at least two hours before serving. Two to four hours is the sweet spot for texture and flavor.

Stir gently before serving and taste again for seasoning. Serve cold as a side dish next to burgers, grilled chicken, hot dogs, or any summer barbecue plate. A light sprinkle of extra dried dill on top makes it look finished.