1 (28 oz.) can whole peeled tomatoes, with juices
1 onion, peeled and halved
5 tbsp. unsalted butter
Salt, to taste
Combine the tomatoes, onion, and butter in a medium saucepan over medium heat. Bring the mixture to a simmer, then reduce the heat to keep the sauce at a low, steady simmer for 45 minutes. Stir occasionally, crushing the tomatoes against the side of the pot with a wooden spoon. Remove from the heat, discard the onion, and add salt to taste. (I didn’t add any salt.) Serve warm with pasta.