This classic all-purpose tomato sauce is simple and quick to make. It relies on the best canned tomatoes (we use Italian San Marzano) and really good extra virgin olive oil. It is the all-purpose sauce that we use for spaghetti, lasagna, and pizza. At this point we all know it by heart—we hope you will too. Castelvetrano olives, from Sicily, add a delightful brininess that brightens the sauce in ways fresh lemon or sugar can only dream of doing.
Pour the tomatoes into a heavy medium pot. Rinse the can with 1/2 cup water and add it to the pot. Add the onions, garlic, basil, olives, pepper flakes and olive oil. Season with salt and pepper. Simmer over medium-low heat, stirring occasionally, until the onions are soft and the sauce thickens, about 30 minutes. Adjust the seasonings and add a little more olive oil if you want to reduce the acidic flavor of the sauce. Remove and discard the onions and basil before using.