In a large bowl, combine the buttermilk and sour cream. Stir until well mixed.
Add the grated beets, diced cucumber, chopped dill, sliced radishes, and green onions to the bowl.
Season with salt, pepper, and lemon juice or white vinegar to taste. Mix well.
Refrigerate the soup for at least 1 hour to allow the flavors to meld and to serve it cold.
Enjoy your meal!