Tomato Sauce 2 cups tomatoes, in addition to their juices (for example, a 28-ounce can of San Marzano whole peeled tomatoes) 5 tablespoons butter 1 onion, peeled and cut in half Wrap in a cooking gauze for easier removal  Salt PREPARATION I used fresh Roma Tomatoes. Score the ends of the tomatoes with an “X”. Blanch the tomatoes in boiling…