Heat your olive oil in a large pot over medium heat. Add the diced onion and minced garlic, stirring occasionally until they soften and turn fragrant, about 5 minutes.

Add your Italian sausage and ground beef directly into the pot with the softened onions and garlic. Cook until browned, breaking apart the meat with a spatula.

Drain off most of the excess fat, but leave a small amount behind for flavor.

Pour in your whole tomatoes with their juice, along with the tomato sauce or marinara. Stir in the Italian seasoning, red pepper flakes, salt, and pepper. Let this simmer uncovered for 25 to 30 minutes, stirring occasionally.

Once your sauce has thickened and deepened in flavor, remove about 3 to 4 cups and set it aside to cool. Preheat your oven to 375°F.

In a large bowl, combine your ricotta cheese, 2 cups of the grated mozzarella, Parmesan cheese, egg, salt, and pepper. Mix lightly until everything blends together evenly.

Drain your cooked pasta and rinse it briefly with cool water to stop the cooking process and prevent sticking. Let it cool slightly.

Gently fold your drained pasta into the ricotta cheese mixture until evenly coated.

Pour your cooled meat sauce into the pasta and cheese mixture, folding it in gently until everything is combined without turning into a uniform paste.

Spread half of your pasta mixture into a large baking dish, smoothing it into an even layer.

Top with a portion of your reserved sauce and a layer of mozzarella cheese.

Repeat with the remaining pasta mixture, sauce, and a generous final layer of mozzarella on top.

Place the assembled dish into the preheated oven and bake for about 20 minutes, or until the cheese turns golden and the edges bubble actively.

Let it rest for 5 minutes before slicing to ensure clean servings.