Heat olive oil in a large pot over medium heat.

Add minced onions and crushed garlic to the pot and cook until softened, about 5-7 minutes.

Stir in the tomato paste, canned Italian tomatoes, fresh chopped parsley, oregano, salt, pepper, and sugar.

Bring the sauce to a simmer, then reduce heat to low and simmer gently for about 3 hours, stirring occasionally.

During the last hour of simmering, add meatballs and Italian sausage (if desired) to the sauce.

Cook until meatballs are heated through and sausage is cooked.

Serve the spaghetti sauce over cooked spaghetti.