Step 1: Thinly slice the cucumbers; set aside. If you want them to be in bite-size pieces for the salad, you could cut the slices in half, or even in quarters. It won’t be quite as pretty but it will be easier to eat. You may also peel them if you prefer.
Step 2: Peel onion and cut in half; thinly slice each half. Set aside. (0ptional step)
Step 3: In large measuring cup or bowl, combine sour cream, yogurt, lemon juice, dill, parsley, garlic, green onions, salt, & pepper. Mix until well blended.
Step 4: In large bowl, arrange a layer of cucumbers, followed by a layer of onions. Pour a small amount of sauce over top. Repeat until bowl is full, then pour remaining sauce over the top. Cover and refrigerate for at least 4 hours or overnight. Before serving, carefully mix salad so that all cucumbers are well coated.