Preheat oven to 400Â°F.
Place fish in an ovenproof casserole.
Sprinkle lemon juice over fish.
Dot with butter.
Bake, uncovered, 30 minutes.
Meanwhile, make sauce by combining yogurt, milk, parsley, and dillweed.
After fish has baked 30 minutes, pour sauce over it and continue baking about 30 minutes longer, or until fish flakes.
Garnish with lemon and parsley.