Tomato Sauce with Onion and Butter

This is possibly the simplest tomato sauce I have come across ... the simplest and tasty tomato sauce. I found this recipe on smitten kitchen, which is a site I've begun to visit occasionally. The tastiness must be due to the butter, which is an ingredient I actually rarely use.

Ingredients

• 28 ounces whole peeled tomatoes from a can (San Marzano, if you can find them)
• 5 tablespoons unsalted butter
• 1 medium-sized yellow onion, peeled and halved
• Salt to taste

Instructions

1. Put the tomatoes, onion and butter in a heavy saucepan (it fit just right in a 3-quart) over medium heat. Bring the sauce to a simmer then lower the heat to keep the sauce at a slow, steady simmer for about 45 minutes, or until droplets of fat float free of the tomatoes. Stir occasionally, crushing the tomatoes against the side of the pot with a wooden spoon.
   
2. Remove from heat, discard the onion, add salt to taste.
3. Serve with spaghetti, with or without grated parmesan cheese to pass.

Serves 2-4. Eat.