Sauté the onions over medium heat in the olive oil until they are transparent.
Add the bell peppers, garlic and spices and cook for a five minutes or so longer.
Dump the peppers and onions mixture into your crockpot.
Add the tomatoes, sauce, red wine, tomato paste, salt and pepper to the slow cooker.
Cook uncovered on high for 4 hours or until the sauce reduces about one-third.
Notes
Note: If you don't have a slow cooker, you can cook this sauce on medium heat on top of the stove for about 1 hour, stirring frequently to prevent burning.