In a large bowl, combine ground beef, breadcrumbs, Parmesan, egg, garlic, parsley, salt, and pepper. Mix until just combined. Form into small meatballs (about 1 inch in diameter).
Heat 2 tablespoons olive oil in a large skillet over medium heat. Add the meatballs in batches and brown on all sides. Remove and set aside.
In the same skillet, add 1 tablespoon olive oil. Sauté chopped onion until translucent, about 5 minutes. Add garlic and cook for 30 seconds.
Pour in crushed tomatoes. Add oregano, salt, pepper, and sugar if using. Stir and bring to a simmer.
Return meatballs to the skillet, cover partially, and let simmer for 20–25 minutes, or until meatballs are cooked through and sauce is thickened.
Garnish with fresh basil or parsley and serve hot over pasta or in sandwich rolls.
Notes
Use a mix of ground beef and pork for richer flavor.
For a smoother sauce, blend the crushed tomatoes before cooking.
Meatballs can be baked instead of fried to reduce fat.