Preheat oven to 400°F. Spray foil covered baking tray with non-stick cooking spray. Remove 4 fillets from plastic pouch using corner ez-peel tab. Place the fillets on the tray and bake on middle oven rack for 15 minutes. Turn over and top each fillet with some spaghetti sauce and a slice of mozzarella cheese. Bake for 10 to 12 minutes more or until fillets reach 170°F internal temperature and the cheese has melted.