Preheat your oven to 375°F (190°C).
Cook the ziti pasta according to package instructions until al dente; drain and set aside.
In a large skillet, heat the olive oil over medium heat.
Add the chopped onion and sauté until translucent.
Stir in the minced garlic and cook for an additional minute.
Add the ground beef or sausage; cook until browned.
Pour in the marinara sauce and Italian seasoning; simmer for 5 minutes.
In a large bowl, combine cooked ziti, ricotta cheese, and half of the mozzarella cheese.
Spread half of the meat sauce in a baking dish, then layer with the ziti mixture.
Top with remaining meat sauce and sprinkle with Parmesan and remaining mozzarella.
Cover with foil and bake for 30 minutes.
Remove foil and bake for another 15 minutes until cheese is bubbly and golden.
Let cool for a few minutes before serving.