Makes 4 cups
- 1/4 cup extra-virgin olive oil
- 1/2 cup minced yellow onion
- 2 1/2 lb ripe plum tomatoes, peeled, seeded, and coarsely chopped
- Kosher salt, as needed
- Heat the oil in a large saucepan over low heat.
- Add the onions and cook, stirring frequently, until tender and translucent, then add tomatoes.
- Season the sauce lightly with salt and simmer the sauce until it is thickened and flavorful, 20 to 30 minutes.
- When the sauce is cooked, pass it through a food mill. The sauce is ready to use now or it can be cooled and stored in covered containers in the refrigerator for up to 4 days.