I had intended to use Cento canned Italian tomatoes to make Marcella Hazan's Tomato Sauce With Onion & Butter, but Whole Foods only had Isola canned Italian tomatoes and bonus, they were on sale. I thought about melting the butter first and sauteeing the onion and garlic and then adding the tomatoes but I suspected that by adding it all at once to the pot, the butter melting would somehow soften the acid of the tomatoes and also the bite of the garlic. I was right. The result was a deeply flavorful, yet mellow red sauce. —Oralia Anderson
Put the canned tomatoes in a saucepan, add the butter, onion, garlic, salt and pepper and cook, uncovered, at medium-low heat until sauce begins to slightly bubble, then adjust heat to low and continue to cook at a very slow, but steady simmer for 45 minutes, or until it is thickened to your liking.
Stir from time to time, mashing up any large pieces of tomato with the back of a wooden spoon.