In a bowl, add sour cream, Miracle Whip®, dill, vinegar, sugar, salt and pepper; stir until well combined and set aside.
Using a mandolin, slice cucumber thinly and set aside. Slice onions (Lyonnaise cut) thinly and halve the slices.
In a large bowl, combine cucumbers and onion slices. Pour half of the dressing over and stir well until veggies are well coated. Slowly add more dressing until desired consistency. Cover and transfer to the refrigerator for at least 1 hour before serving.