To prepare the meatballs, preheat oven to 375°. Line a rimmed baking sheet with foil. Place a wire rack over pan, and spray with cooking spray. In a large bowl, combine beef, sausage, egg, bread crumbs, grated onion, Parmesan, 1/2 teaspoon salt, pepper, and garlic powder. Shape mixture into 2” balls. Place on prepared rack. Bake for 10 minutes.