Classic Tomato Sauce

Classic Tomato Sauce
Makes about 3 cups sauce, enough for 1 1/2 pounds of pasta.

1 (28-ounce) can Italian whole peeled tomatoes (San Marzano style tomatoes are best, any brand)
6 tablespoons unsalted butter
1 medium onion, peeled and cut in half
Kosher salt
1 to 1 1/2 pounds pasta
Parmesan cheese, to serve, optional

1. Fill a large pot 2/3 full with water, cover with a lid, and set over high heat. If it comes to a boil before the pasta is done, reduce the heat to low until ready to cook the pasta.
2. Place the tomatoes in a medium bowl. Remove basil leaves from the tomatoes and discard them. Mash up the whole tomatoes with your hands or cut them using two knives.
3. Place the crushed tomatoes, 5 tablespoons of the butter, onion halves (cut side down), and two big pinches of salt in a large saucepan. Cook, uncovered, at a very slow but steady simmer for 45 minutes, or until the fat floats to the top. Stir it from time to time, mashing any large pieces of tomato in the pan with the back of a wooden spoon or a fork. Discard the onion. Taste and season with salt and pepper. If you are using 1 pound of pasta, remove about one-third of your sauce for another time. If using 1.5 pounds pasta, use all the sauce.
4. Now that the sauce is ready, it’s time to boil the pasta: to the pot of boiling water, slowly stir in enough salt so that the water tastes like the ocean - you’ll need to sample the water with a spoon, and will probably use a big handful of salt. (Make sure you add the salt slowly, as it sometimes bubbles over.) Let the water come back to the boil, drop in the raw pasta and gently stir so the pastas don’t stick together. Follow the packaging directions, reducing the time, though, by 2 minutes to start checking for al dente. Al dente means “to the tooth” in Italian — soft enough to easily bite into, but with some firmness on the inside of the noodle. (In other words, you don’t want it flabby throughout.)
5. Once your pasta is done, it’s time to sauce the pasta: you have two options: you can either lift it out using a pasta spoon or a spider, or you can drain the water out through a strainer. If you use the strainer method, you must scoop up and save about 1 cup of the pasta cooking water….this is the key to finishing your sauce. It’s what helps make a sauce delicious. Why? Because this water is starchy (it’s floury and it helps thicken the sauce) and it’s also salty. So it gives the sauce added flavor and texture. 
6. Once drained from the pasta cooking water, place the pasta directly into your sauce, along with the remaining 1 tablespoon butter, then toss it over low heat until the sauce is the right consistency. If it’s too loose, keep simmering and stirring the pasta. If it’s too thick, add a little pasta water. Serve right away with Parmesan cheese. Recipe adapted from “Essentials of Classic Italian Cooking” by Marcella Hazan.

NOTE: Before boiling your pasta, it’s a good time to look around your kitchen to see if there are any vegetables that need blanching…green beans, broccoli florets, you name it. Use the salted water for other cooking tasks before you add the pasta.