400g can of whole, peeled tomatoes
One peeled, halved onion
5 tablespoons (71g) of butter.
A pinch or two of salt
Put everything together in a single pot and set it to simmer over medium heat on the stove for 45 minutes, uncovered. Give it the occasional stir.
And that's it. After the 45 minutes is up, toss out the onion halves, and pour the sauce over your favorite pasta. Easy.