1. Cook the rigatoni in salted boiling water until just under al dente. Reserve 1/2 cup of pasta water and drain.

2. In a large skillet, heat olive oil and sauté diced onion until softened.

3. Add garlic and cook for 1 minute until fragrant.

4. Add ground beef and cook until browned, breaking it up with a spoon.

5. Stir in crushed tomatoes, Italian seasoning, red pepper flakes, and reserved pasta water. Simmer for 8-10 minutes.

6. Season the sauce with salt and pepper to taste.

7. Add the cooked pasta to the sauce and stir to combine fully.

8. Transfer the pasta mixture to a greased ceramic baking dish.

9. Top with shredded mozzarella and sprinkle with parmesan cheese.

10. Bake at 375°F for 20 minutes, then broil for 2-3 minutes until golden and bubbly.

11. Remove from oven, garnish with fresh parsley, and let rest for 5 minutes before serving.