Cook rigatoni according to package directions until al dente, about 9-11 minutes. Drain and set aside, reserving 1/2 cup pasta water for later if needed. This prevents overcooking since the pasta will finish cooking in the oven.

Heat olive oil in a large skillet over medium-high heat. Add diced onion and sauté for 3-4 minutes until softened and fragrant, then add minced garlic for another minute. Brown the ground beef thoroughly, breaking it into small pieces as it cooks, about 6-8 minutes total.

Stir in the crushed tomatoes and tomato paste, mixing well. Add dried oregano, basil, salt, pepper, and red pepper flakes, simmering for 10 minutes. Let the sauce develop its rich flavors while you prepare the cheese mixture.

In a separate bowl, combine ricotta cheese, shredded mozzarella, grated parmesan, egg, salt, and pepper. Mix until smooth and well combined, adjusting seasonings to your taste preference.

Your cozy baked rigatoni warm recipe now comes together beautifully in a 9x13 baking dish. Spread half the meat sauce on the bottom, layer half the cooked pasta, then half the cheese mixture, then repeat layers ending with cheese on top.

Bake uncovered at 375°F for 35-45 minutes until the top is golden brown and bubbling at the edges. Let rest for 5 minutes before serving to allow the dish to set slightly and prevent it from falling apart.