1. Preheat the oven to 375°F (190°C).

2. Cook the penne pasta according to the package instructions until al dente. Drain and set aside.

3. In a large saucepan, melt the butter over medium heat.

4. Add the gluten-free flour and cook for 1 minute, stirring constantly.

5. Slowly whisk in the 1% low-fat milk, stirring until smooth and thickened.

6. Stir in the canned chopped tomatoes and cook for an additional 2 minutes.

7. Add the American cheese and mozzarella cheese, stirring until melted and well combined.

8. Season with salt and pepper to taste.

9. Add the cooked penne pasta to the saucepan and toss to coat evenly with the cheese sauce.

10. Transfer the mixture to a greased baking dish.

11. Bake in the preheated oven for 20 minutes or until bubbly and golden brown on top.

12. Serve hot and enjoy!