Cook spiral pasta noodles according to package instructions. While pasta is cookibg, in a large skillet over medium heat, brown ground beef and onion together ground beef is no longer pink; drain fat. Stir in spaghetti sauce and pasta, once noodles are cooked and drained.
Spray 2 9"x13" baking casseroles with non-stick cooking spray, and divide mixture into both casseroles evenly. Sprinkle each with cheese and top with pepperoni.
Cool if needed, then cover and freeze.
On cooking day
Thaw casserole in fridge overnight. Bake at 350F for 35-40 minutes or until heated through.