Thinly slice the cucumbers into 1/8-inch rounds and place them in a colander. Thinly slice the red onion into half moons. Let the cucumber slices sit in the colander for 5 minutes to allow excess moisture to drain—this prevents the salad from becoming watery. While the cucumbers drain, finely chop the fresh dill and set aside.

In a medium bowl, whisk together the sour cream and mayonnaise until smooth. Add the white vinegar, lemon juice, onion powder, garlic powder, sugar, and celery salt. Whisk until all seasonings are fully incorporated and the dressing is uniform. Taste and adjust seasoning with salt and freshly cracked black pepper to your preference. I like to add the salt gradually since the celery salt already brings some saltiness—you can always add more but you can't remove it.

Pat the drained cucumber slices dry with paper towels to remove any remaining moisture. Add the dried cucumbers, sliced red onion, and chopped dill to the bowl with the creamy dressing from Step 2. Gently fold everything together until all the vegetables are evenly coated with the dressing. I recommend serving the salad immediately while the cucumbers are still crisp, though you can refrigerate it for up to 2 hours if needed—just know the cucumbers will soften slightly over time.