Drain reserving 1 cup of pasta water, cover and set aside.
Preheat oven to 375 degrees F.
In large skillet over medium heat, cook beef, onion and garlic; stirring frequently 6 to 8 minutes or until beef is browned. Drain fat.
Stir in 5 cups spaghetti sauce and reserved pasta water. Reduce heat and simmer 10 minutes. Mix the meat/sauce mixture with ziti.
Spoon ½ of ziti mixture into 13x9x2" baking dish. Sprinkle with Mozzarella and ½ of Parmesan cheese.
Top with remaining ziti mixture and remaining 1 cup spaghetti sauce. Sprinkle with remaining Parmesan cheese. Bake for 25 - 30 minutes or until heated through.