Good recipe for any filleted fish. If using other fish, cook time may vary depending on the type and thickness of fillets.
Preheat oven to 350 degrees F (175 degrees C). Grease a baking pan with vegetable oil.
Place mackerel fillets in the baking pan; season with salt and pepper.
Mix butter, lemon juice, and paprika together in a bowl. Pour over mackerel fillets.
Bake in the preheated oven until mackerel flakes easily with a fork, 20 to 25 minutes.