1.Preheat your oven to 375°F (190°C). Grease a 9×13-inch baking dish.
2.In a large mixing bowl, combine ground beef, breadcrumbs, grated Parmesan cheese, milk, chopped onion, egg, salt, black pepper, garlic powder, dried oregano, and dried basil. Mix until well combined.
3.Form the mixture into meatballs, about 1 to 1.5 inches in diameter.
4.Cook the spaghetti according to the package instructions until it’s al dente. Drain and set aside.
5.In a large skillet, heat some olive oil over medium heat. Add the meatballs and brown them on all sides. They don’t need to be cooked through at this point, as they’ll finish cooking in the oven.
6.Spread half of the marinara sauce in the bottom of the greased baking dish.
7.Place the cooked spaghetti on top of the sauce.
8.Pour the remaining marinara sauce over the spaghetti and gently toss to coat.
9.Arrange the browned meatballs on top of the spaghetti.
10.Sprinkle shredded mozzarella cheese and grated Parmesan cheese evenly over the top.
11.Cover the baking dish with aluminum foil and bake for 25 minutes.
12.Remove the foil and bake for an additional 10-15 minutes or until the cheese is melted and bubbly, and the meatballs are cooked through.
13.If desired, garnish with fresh basil leaves before serving.