Cook ground beef in a saucepan over medium-high heat with garlic, onion, and green pepper. Stir until the meat is brown and crumbly. The vegetables should be tender.
Stir diced tomatoes, tomato sauce, and tomato paste into the beef mixture. Add oregano, basil, salt, and pepper. Simmer until thick and aromatic, then serve over cooked spaghetti noodles.
