Saute onion and green pepper in oil until translucent; remove from heat. Add seasonings; allow to sit for 10-15 minutes for flavors to blend.
Combine tomato sauce, tomato paste, and brown sugar in large pot. Add vegetable/seasoning mixture; stir until combined. Simmer for 1-2 hours.
(Alternatively, this sauce could be cooked in a slow cooker for about 4 hours on low heat.)
Allow to cool completely. Freeze as desired.