On medium high, melt butter in small sauce pan. Add the onions, bell pepper and tomato. Let veggies saute in butter for about 2-3 minutes.
Add Tomato sauce, ketchup and water. Stir and add the cumin. Add salt to taste, add cilantro and let simmer for about 5-7 minutes or until the sauce has thickened enough to cover the back of a metal spoon when dipped in the sauce.
Serve on top of cabbage salads or on the side as a dipping sauce.