In a heavy saucepan, melt the butter. Sauté the onion and garlic in the butter until translucent, about 10 minutes. Add all the remaining ingredients and simmer for about 15 minutes, until the flavors have blended. Continue cooking until the sauce begins to thicken, 20 to 30 minutes. Taste and adjust the seasonings with salt and pepper if desired. Remember, the ribs will have plenty of spice rub on them, so don’t overseason the sauce.
Let the sauce cool for about 10 minutes or until it is warm but no longer “boiling” hot. Puree with an immersion or traditional blender—this will make the sauce thicker. Let cool. The sauce will keep, tightly covered, in the refrigerator for up to 2 weeks.
Brush it on food 5 to 15 minutes before the cooking time is finished. If desired, serve extra on the side.