Preheat oven to 375 degrees F. Lightly grease a 9 x 13-inch pan with non-stick cooking spray.
Cook ziti about 2 to 3 minutes less than package directions for al dente pasta. Drain, rinse with cold water to stop the cooking and set aside.
In a large bowl, mix marinara sauce, ricotta and 1 cup of mozzarella.
Pour about 2 cups of the sauce mixture in prepared pan, spreading over bottom.
Combine ziti and remaining sauce mixture and stir until well combined, making sure there are no dry patches of pasta. Pour into pan and spread to edges.
Sprinkle remaining mozzarella over ziti to cover.
Spray a sheet of aluminum foil with cooking spray and cover ziti. This will keep the cheese from sticking to the foil.
Bake, covered, at 375 degrees for 45 minutes to 1 hour. Uncover and continue baking until cheese is golden brown and bubbly.
Serve hot, straight out of the pan.