Baked Mackerel with Onion and Tomato

Heat the oven to 425°F. Arrange fillets in an oiled baking dish, skin side down, and brush them with olive oil and lemon juice. Sprinkle with salt, pepper, garlic powder, and thyme. Combine onion and tomatoes and spoon them over and around the fillets. Bake for 10 minutes per inch thickness of fish.