Tomato sauce with Italian sausage

How I make this.

Little bit of extra virgin olive oil in a pot. Throw a pound of your favorite kind of Italian sausage in the pot to cook it. Take sausage out once it’s cooked. Chop onion in half. Little bit more extra virgin olive oil if there’s not a lot of fat from the sausage left. Throw onion halves in the pot. Add a few dollops of tomato paste and fry them for a few minutes. Throw in as many garlic cloves as you want and fry them till they brown a little bit. If the onion layers start separating, no big deal. Still easy to take them out later. Throw your sausage back in. Crush 2 28oz cans of San Marzano tomatoes and toss them in the pot. Cut off your parmigiano reggiano rind with a tiny bit of cheese left on it and throw it in the pot. After an hour and half or so of simmering take the onion and rind out. Same with the garlic or you can smash it in the pot and stir. Simmer till the sauce is the right thickness. Toss in a 1/3 of a stick of unsalted butter, stir. Salt to taste.