Place whiting fillets in a baking dish and add enough milk to cover the entire bottom of the dish. Season fillets with garlic powder, onion powder, paprika, and salt. Top each fillet with at least 3 pieces tomato. Add butter to each fillet. Squeeze 1 lemon half over each fillet.
Bake in the preheated oven until fish flakes easily with a fork, 30 to 45 minutes.
