This very simple sauce can be made in advance and frozen in 2-cup containers so you can pull it out at the last minute from the freezer to use in a multitude of ways.
Heat olive oil in large Dutch oven over medium heat. Add garlic and onion and cook, stirring, until tender, 5 to 6 minutes. Add the Italian seasoning and cook for 30 seconds. Add the diced tomatoes with juice, the tomato puree and parsley, Stir to blend. Reduce the heat to low and simmer for 1 hour.