Preheat the oven to 350 degrees F (175 degrees C).

Place the pre-cooked crust on an ungreased 12-inch pizza pan. Spread pizza sauce over the crust and top with garlic powder, Italian seasoning, Parmesan cheese, and onion, in that order. Arrange meatball slices and pepperoni on top. Sprinkle pizza with mozzarella cheese and Cheddar cheese.

Bake in the preheated oven until heated through and cheese is melted, 12 to 17 minutes.