Heat the oven to 375°F (190°C) and lightly grease a 9-by-13-inch baking dish.

Bring a large pot of well-salted water to a boil. Cook the ziti until just shy of al dente, usually about 2 minutes less than the package directions, then drain well.

Heat the olive oil in a large skillet or Dutch oven. Cook the onion for 4–5 minutes until softened, add the garlic, and cook for about 30 seconds.

Add the ground beef, Italian sausage, or combination and cook until browned, breaking it into small pieces. Drain excess fat if necessary.

Stir in the marinara sauce, crushed tomatoes, Italian seasoning, red-pepper flakes, salt, and black pepper. Simmer for 10–15 minutes.

Combine the ricotta, egg, 1/2 cup Parmesan, and about 1 cup mozzarella in a bowl.

Toss the drained pasta with roughly two-thirds of the meat sauce.

Layer half the pasta in the baking dish, spoon over half the ricotta mixture, and add some of the remaining sauce and mozzarella. Repeat with the remaining pasta, ricotta mixture, sauce, mozzarella, and remaining Parmesan.

Cover tightly with foil and bake for 20 minutes. Remove the foil and bake for another 10–15 minutes, until bubbling and lightly browned.

Rest the baked ziti for 10–15 minutes before serving. Garnish with chopped parsley or basil.