The Simplest Tomato Sauce Ever (Marcella Hazan)

Combine the tomatoes, their juices, the butter, and the onion halves in a medium saucepan.

Add a pinch or two of salt. Place over medium heat and bring to a simmer. Cook, uncovered, at a very slow but steady simmer, adjusting the heat as necessary, for about 45 minutes, or until droplets of fat float free from the tomato.

Stir occasionally, mashing any large pieces of tomato with the back of a wooden spoon. Taste and salt as needed.

Discard the onion.