01 -
Preheat oven to 375°F (190°C) and line a baking sheet with foil for easier cleanup. Spray with cooking spray.
02 -
In a large bowl, combine ground beef, onion, egg, garlic, breadcrumbs, Italian seasoning, salt, pepper, and crushed red pepper flakes. Mix gently with hands or a wooden spoon. Do not overmix to prevent tough meatballs.
03 -
Using a medium cookie scoop (1-2 tablespoons size), form approximately 32 meatballs. Arrange them evenly on the prepared baking sheet and bake for 15 minutes, or until cooked through (larger meatballs may require up to 20 minutes).
04 -
Spray a 2.5 to 3-quart casserole or baking dish (or 9x13-inch pan) with cooking spray. Add cooked meatballs to the dish.
05 -
Evenly drizzle marinara sauce over the meatballs, then sprinkle mozzarella and Parmesan cheeses on top.
06 -
Bake uncovered for 10-15 minutes, or until the cheese has melted and is lightly golden browned as desired.
07 -
Optionally garnish with fresh basil or parsley. Serve immediately.