Copyright Mark Bittman: How to Cook Everything Vegetarian
3 tablespoons olive oil or butter
1 medium onion, chopped
One 24- to 32-ounce can tomatoes, drained and chopped
Salt and freshly ground black pepper
Freshly grated Parmesan or other cheese (optional)
Chopped parsley or fresh basil leaves for garnish (optional)
Put the olive oil in a 10 or 12-inch skillet over medium-high heat. When hot, add the onion nad cook, stirring occasionally, until soft, 2 or 3 minutes. Add the tomatoes, along with a sprinkling of salt and pepper.
Cook, stirring occasionally, until the tomatoes break up and the mixture comes together and thickens (10 to 15 minutes). Taste, adjust the seasoning, and immediately toss with pasta (garnish with cheese or an herb if you like) or use in other dishes. Or cover and refrigerate for up to several days (reheat gently before serving).