This will make enough sauce for half-pound to one-pound of pasta, depending on preference.
Cut an X in bottom of each tomato and blanch in a large pot of boiling water 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, and 1/2 teaspoon salt and simmer, covered, stirring occasionally, 45 minutes - 1 hour. Season with salt, to taste.