- Preheat your oven to 400°F. 
- Cook the rigatoni in salted water until just shy of al dente. Drain and set aside. 
- In a large skillet, heat the olive oil. Add diced onion and sauté until soft. Toss in the garlic and stir for about 30 seconds. 
- Add sausage to the skillet and cook until browned. Break it up with your spoon as you go. 
- Pour in the crushed tomatoes, salt, pepper, oregano, and red pepper flakes. Let it simmer for 10 minutes. 
- Stir in the heavy cream and simmer another 5 minutes. Turn off the heat and mix in the Parmesan. 
- Combine cooked pasta with the sauce in a large mixing bowl. Add half the mozzarella and stir. 
- Transfer everything to a greased 9x13 baking dish. Sprinkle remaining mozzarella on top. 
- Bake uncovered for 20 minutes, or until the cheese is bubbly and golden. 
- Let it cool for 5–10 minutes before serving. Garnish with fresh basil if you're feeling fancy.