Start by prepping all your ingredients—chop the onions, mince the garlic, and dice the bell pepper.
In a large saucepan over medium-high heat, combine ground beef, onion, garlic, and green bell pepper. Cook for 5-7 minutes, breaking up the beef with a wooden spoon, until the meat is browned and the veggies are soft. Drain any excess grease.
Add in the diced tomatoes, tomato sauce, and tomato paste. Stir everything together until well combined.
Sprinkle in the oregano, basil, salt, and black pepper. Stir to evenly distribute the seasonings.
Lower the heat to a gentle simmer. Cover the saucepan and let the spaghetti sauce cook for 1 hour, stirring occasionally to prevent it from sticking to the bottom.
After an hour, taste the sauce and adjust the seasoning if necessary. Serve hot over your favorite pasta and enjoy!