Cook on low for around 10 hours. The sauce should reduce by around half in volume compared to raw ingredients.
An immersion blender is our preferred method to mix up the sauce appropriately
To thicken the sauce up, canned tomato paste can be added
1 can tomato paste
Add the baking soda, salt and pepper to taste.
1/8 tsp baking soda, salt and pepper
Allow to cool or better yet let it refrigerate overnight to allow the flavors to embed into the sauce.
Notes
Skin removal of the tomatoes is a job task which is much easier with 2 people doing it The introduction of baking soda will most likely make things foam up and look a bit strange.