As you can see from the ingredient list, everything about this recipe depends on the quality of the tomatoes. The preferred tomatoes, from the famed San Marzano region of Naples, are deep red, firm, and meaty, with very few seeds. They are low in acid and high in fruitiness because they are handpicked when they are fully ripened. Although Roberto uses only imported brands, in particular the Francesconi brand, you’ll find both imported and domestic brands on the market. American tomato growers have cultivated the seeds and are growing and canning San Marzano tomatoes in the United States.