Instructions: Heat oil in a large, heavy-bottomed saucepan over medium heat until shimmering but not smoking. Add onion and saute until golden brown, about 10 minutes, stirring frequently. Add remaining ingredients, cutting tomatoes in half or quarters. Bring to boil, reduce heat to lowest possible setting and simmer, uncovered until thickened, about 2-2 1/2 hours.

Puree sauce, in batches if needed, in blender. Use immediately or cover in airtight container. Sauce can be refrigerated for up to 2 weeks or frozen for several months.

Variations:
Sauce with Mexican flavors: To classic sauce, add 1 1/2 teaspoons ground cumin, 1 1/2 teaspoons chili powder, 6 tablespoons lime juice, and 3 tablespoons chopped fresh cilantro.

Sauce with Asian flavors: Add 1 tablespoon minced, fresh ginger, 6 tablespoons soy sauce, 6 tablespoons rice vinegar, 3 tablespoons sugar and 1 1/2 tablespoons Asian sesame oil to classic sauce.

Sauce with Caribbean flavors: Add 2 tablespoons pineapple juice, 2 tablespoons dark rum, 1 tablespoon Caribbean hot sauce, 2 teaspoons sugar and a pinch of ground allspice to classic sauce.

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