This classic sauce is perfect over pasta or as a dipping sauce for garlic bread. You can even add sausage or ground meat if you like.
Heat the olive oil in a large pot over medium heat. Add the onion and garlic and cook until soft, about 6-7 minutes. Add in the plum tomatoes, basil leaves, sugar, and season with salt and pepper. Bring to a simmer, and cook for 30 minutes, until the sauce has thickened, stirring often. Remove the pan from the heat, cover, and let stand 15 minutes.
If desired, pass the sauce through a food mill or chop it in a blender or food processor until in small pieces. If desired, the sauce can be cooled and refrigerated up to 4 days, or frozen up to 6 months.