Combine sour cream, greek yogurt, lemon juice, minced garlic, and dill in a small bowl. Add salt and pepper to taste. Stir and set aside.
Slice tomatoes into wedges. Place in a large mixing bowl. Add thinly sliced red onion. Just before serving, stir the sauce into the salad and mix to coat.
Garnish with dill and green onions.
After adding the sauce, the salad will stay fresh for about 5-6 hours if refrigerated.
