Preheat oven to 350F degrees. Spray a 9x13 baking dish with nonstick spray. Prepare pasta according to directions. In a medium sauce pan, brown ground beef with onion (if using). After beef is brown and crumbled, drain excess grease. Put back in pot and pour in one jar of spaghetti sauce. Keep mixture on low until pasta is done. When pasta is finished, drain excess water from pasta. You want the pasta as dry as possible. Put pasta back in large pot (with heat off) and pour in jar of alfredo sauce. Combine until thoroughly coated. Pour pasta mixture into bottom of 9x13 dish. Cover pasta with spaghetti sauce mixture. Don’t put the pot that you used for the spaghetti sauce in with the dirty dishes yet. Keep that pot out and start heating up second jar of spaghetti sauce on low heat. Put a cover on it to keep warm until ziti is finished baking. Sprinkle top with mozzarella cheese. Cover with aluminum foil and bake for 15 minutes. I like to spray the inside of my foil with nonstick spray so the cheese doesn't stick to it. Remove foil and bake for another 15 minutes until cheese is melted and bubbly