Add olive oil to large dutch oven and heat over medium heat until oil is just shimmering. Meanwhile roughly chop 2 medium onions. Saute onions until soft and just beginning to caramelize.
Add tomatoes and the remainder of the seasonings to the dutch oven and simmer for 4 hours. At this point the tomatoes will be broken up and the sauce will be chunky.
Remove stems from basil and oregano.
If a smoother sauce is desired, use an immersion blender to puree until smooth and continue to simmer for another hour.
Use immediately or cool completely and store in quart size freezer containers and freeze until ready to use.
This recipe is easily cut in half.