2 tablespoons extra-virgin olive oil
1 small white onion, finely chopped
1 medium carrot, grated
One 28-ounce can whole plum tomatoes in juice, coarsely pureed
1 tablespoon unsalted butter
2 teaspoons fresh oregano, finely chopped
In a medium saucepan, heat the olive oil over moderate heat until shimmering. Add the onion and cook, stirring, until softened, about 8 minutes. Stir in the carrot, then add the tomatoes and season with salt. Simmer over moderately low heat, stirring occasionally, until the sauce has thickened, about 40 minutes. Remove from the heat and stir in the butter and oregano.
The tomato sauce can be refrigerated for up to 1 week.