Cut an X in the bottom of each tomato and blanch in a large pot of boiling water for 10 seconds. Immediately transfer tomatoes with a slotted spoon to an ice bath to cool, then peel, seed and chop. Cook garlic in oil in a small, heavy pot over medium heat, stirring occasionally until golden, 3 to 5 minutes. Add tomatoes, red pepper flakes, season with salt and pepper and add fresh basil. Cover and simmer for 1 hour, stirring occasionally.
If ripe tomatoes are not available, substitute 1 (28-ounce) can diced tomatoes in juice; season sauce with sugar if desired. (preferred brand: Organic Muir Glen)