Thinly slice cucumbers using a mandoline (or very sharp knife) and place in a large bowl. Sprinkle with salt, and stir very well to combine. Allow to rest for 30 minutes (or more).
Rinse cucumbers (to remove salt). Strain, or dry with a tea towel (or paper towels), squeezing lightly to remove liquid.
Add cucumbers and onion to a medium bowl. Add sour cream, dill, and pepper. Stir well to combine.
Allow to rest for about 30 minutes, or until ready to serve. Stir, taste, and add additional salt to taste. Garnish with dill if desired.
Notes
Substitute ½ tablespoon table salt for kosher salt (in step 1), if needed.
A mandoline, or a sharp knife, work well for consistent, thinly sliced cucumbers and red onions.
Stir together the sour cream, chopped dill, and pepper in a small bowl first. This makes mixing the ingredients together easier.
Refrigerate leftovers for about 3 days.
Note: 3 Tablespoons fresh herbs = 1 teaspoon dried herbs.