In a large saucepan, heat oil over medium-high heat. Add onions; cook and stir until tender, 3-5 minutes. Add garlic; cook and stir 1 minute longer. Stir in remaining ingredients. Bring to a boil. Reduce heat; cover and simmer until thickened and flavors are blended, 30-45 minutes, stirring occasionally and breaking up tomatoes with wooden spoon.