Preheat your oven to 375°F (190°C) for even baking.

In a large skillet, heat olive oil over medium heat. Add diced onion and minced garlic, sauté for 3 to 4 minutes.

Add Italian sausage and ground beef, breaking apart as they cook for 6 to 8 minutes. Drain excess fat.

Stir in whole tomatoes, tomato sauce, Italian seasoning, red pepper flakes, kosher salt, and ground black pepper. Simmer for 10 to 15 minutes.

Bring salted water to a boil and cook ziti for about 2 minutes less than package instructions for al dente. Drain and return to pot.

In a bowl, combine ricotta cheese, mozzarella, Parmesan, egg, and a pinch of salt and pepper. Blend until semi-combined.

Add cooked ziti to the cheese mixture and toss gently to coat. Stir in a few cups of the sauce until pasta is just covered.

In your baking dish, layer half of the pasta mixture, mozzarella, and sauce. Repeat with remaining ingredients.

Cover with foil and bake for 30 minutes. Remove foil and bake uncovered for an additional 15 minutes.

Let cool for 5 minutes before slicing. Garnish with parsley and serve.