In a large, heavy saucepan, melt the butter with the oil over medium heat. Add the onion, and sauté until slightly caramlized, about 5 min.
Add the garlic and sauté another 2 min. Add all the remaining ingredients, raise the heat, and cook at a full boil for 10 min., stirring frequently.
Reduce heat, partially cover,and simmer for 30 min., stirring occasionally. Sauce may be refrigerated and reheated when needed.Yields: 3-4 cups