Heat oil in large dutch oven over medium heat. Add onions. Saute until they start to brown.
Add minced garlic. Heat until fragrant.
Add both cans of tomatoes (with juice) and salt and pepper. Reduce heat and cook on low for 30 to 45 minutes. (I like a fresh, more astringent flavor in my sauce, so I cook it for the least amount of time. If you're looking for a deep, robust flavor cook it longer.)
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