Preheat oven to 400°F.
Place fish in casserole.
Sprinkle lemon juice over fish.
Dot with butter and season with salt and pepper.
Bake, uncovered, for 30 minutes in preheated oven.
Meanwhile, make sauce by combining yogurt, milk, parsley and dill.
After fish has baked for 30 minutes, pour sauce over it and continue baking for approximately 30 minutes longer or until fish flakes.
Garnish with lemon and parsley.