Step 1

Combine cucumber and onion in a colander set over a large bowl. Toss with 3/4 teaspoon of the salt. Let stand, tossing occasionally, until softened and liquid has drained out, about 1 hour. Pat vegetables dry with paper towels.

Step 2

Meanwhile, stir together sour cream, vinegar, dill, chives, and remaining 1/4 teaspoon salt in a medium bowl. Add cucumber and onion mixture; toss to coat. Serve sprinkled with pepper, dill, and chives.