Make the Meatballs:
In a large bowl, combine the ground beef, breadcrumbs, grated Parmesan, egg, minced garlic, parsley, oregano, basil, salt, and pepper. Mix until just combined.
Form the mixture into 1 to 1.5-inch meatballs and place them on a baking sheet.

Cook the Meatballs:
Heat a large skillet over medium heat and add a little olive oil. Working in batches, cook the meatballs for 5-6 minutes, turning them occasionally until they’re browned on all sides. Once browned, remove them from the skillet and set aside.

Prepare the Tomato Sauce:
In the same skillet, add 2 tablespoons of olive oil and heat over medium heat. Add the chopped onion and minced garlic, and sauté for 3-4 minutes until softened.
Stir in the crushed tomatoes, oregano, basil, salt, pepper, and red pepper flakes (if using). Bring the sauce to a simmer.

Simmer the Meatballs:
Return the meatballs to the skillet with the tomato sauce. Spoon some sauce over each meatball, cover the skillet, and simmer for 20-25 minutes, until the meatballs are cooked through and the sauce is flavorful.

Serve:
Remove the skillet from the heat. Garnish with fresh basil and serve the meatballs with your favorite pasta, rice, or bread.