1. Preheat the oven to 375°F (190°C).

2. In a large pot, bring water to a boil and cook the penne according to package instructions. Drain and set aside.

3. In a separate pot, melt the butter over medium heat. Stir in the gluten-free flour and cook for 2 minutes, until lightly browned.

4. Gradually whisk in the milk and continue cooking until the sauce thickens, about 5 minutes.

5. Stir in the allspice, accent seasoning, salt, and pepper to taste.

6. Add the shredded cheddar cheese and stir until melted and smooth.

7. In a greased baking dish, combine the cooked penne, canned chopped tomatoes, green beans, and black beans. Mix well.

8. Pour the cheese sauce over the penne mixture and stir to coat evenly.

9. In a small bowl, mix together the baking powder and applesauce. Pour this mixture over the penne mixture.

10. Bake in the preheated oven for 25-30 minutes, or until bubbly and golden brown on top.

11. Serve hot and enjoy!