Step 1

Put a large colander in a large bowl. Add the cucumbers and onions to the colander, sprinkle with 1 tablespoon salt and toss until the salt is evenly distributed. Let stand at room temperature for at least 1 hour and up to 2 hours.

Step 2

Transfer the cucumbers and onions from the colander to a paper towel-lined baking sheet and pat them dry with another layer of paper towels.

Step 3

Whisk together the sour cream, dill, vinegar and a few cracks of black pepper in a medium bowl. Add the cucumbers and onions and toss until coated.

Step 4

To make ahead: Salt and pat dry the cucumbers and onions as above, then keep separate from the dressing until ready to serve.