Core the tomatoes and place in the crock pot whole.
Remove the seeds from the green pepper and roughly chop.
Remove the onion skin and roughly chop.
Peel and crush garlic cloves and dice.
Add all the ingredients to your crockpot.
Cook on low for 6-8 hours.
Blend smooth with a stick blender. If you don’t have a stick blender, you can add it to your regular stand blender in batches to process.
Return to the crockpot and cook on low another 6-8 hours, with the lid slightly off to allow steam to escape.
When the sauce is mounded up on a spoon, it is ready. Check taste for seasonings and adjust salt and pepper or sugar as necessary.