Cook the Pasta:

1. Bring a large pot of salted water to a boil and cook the ziti pasta according to package directions until al dente.
2. Drain and set aside.

Make the Meat Sauce:

1. Heat a large skillet over medium heat and cook the ground beef until browned, breaking it apart with a spoon.
2. Add the diced onion and garlic, cooking until softened (about 3-4 minutes).
3. Stir in the marinara sauce, Italian seasoning, salt, and pepper. Simmer for 5 minutes, then remove from heat.

Prepare the Cheese Mixture:

1. In a large bowl, combine ricotta cheese, 1/2 cup of shredded mozzarella, Parmesan, egg, garlic powder, and parsley. Mix well.

Assemble the Ziti:

1. Preheat your oven to 375°F (190°C).
2. In a 9×13-inch baking dish, spread a thin layer of meat sauce on the bottom.
3. Layer half of the cooked pasta, then dollop and spread the cheese mixture evenly on top.
4. Add a layer of meat sauce, then repeat with the remaining pasta, sauce, and top with the remaining mozzarella cheese.

Bake the Ziti:

1. Cover the dish with aluminum foil and bake for 25 minutes.
2. Remove the foil and bake for an additional 10-15 minutes, or until the cheese is bubbly and golden brown.

Serve:

1. Let the baked ziti cool for 5 minutes before serving. Garnish with fresh parsley if desired