Step 1

Put either the prepared fresh tomatoes or the canned in a saucepan, add the butter, onion, and salt, and cook uncovered at a very slow, but steady simmer for about 45 minutes, or until it is thickened to your liking and the fat floats free from the tomato.

Step 2

Stir from time to time, mashing up any large pieces of tomato with the back of a wooden spoon.

Step 3

Taste and correct for salt. Before tossing with pasta, you may remove the onion (as Hazan recommended) and save for another use, but many opt to leave it in. Serve with freshly grated parmigiano-reggiano cheese for the table.

Step 4

The blanching method: Plunge the tomatoes in boiling water for a minute or less. Drain them and, as soon as they are cool enough to handle, skin them, and cut them into coarse pieces.

Step 5

The freezing method (from David Tanis, via The Kitchn): Freeze tomatoes on a baking sheet until hard. Thaw again, either on the counter or under running water. Skin them and cut them into coarse pieces.

Step 6

The food mill method: Wash the tomatoes in cold water, cut them lengthwise in half, and put them in a covered saucepan. Turn on the heat to medium and cook for 10 minutes. Set a food mill fitted with the disk with the largest holes over a bowl. Transfer the tomatoes with any of their juices to the mill and puree.