Preparation

• In a 10- or 11-inch sauté pan, heat the oil and onion over medium heat, stirring occasionally, until the onion is softened but not browned, 4 to 5 minutes. Add the pancetta and cook, stirring, until the pancetta has begun to render its fat and the onion and pancetta are roughly the same muted shade of purple, 5 to 6 minutes. Add the tomatoes, cayenne, and salt. Simmer, stirring occasionally and adjusting the heat to maintain a lively but not too vigorous simmer, until the tomatoes have been reduced to a thick, pulpy sauce, 15 to 20 minutes.

To serve with pasta

• While the sauce is cooking, bring a large pot of abundantly salted water to a vigorous boil and cook the pasta until al dente. Drain it well. Taste the sauce and adjust the seasonings if needed. Toss the pasta with three-quarters of the sauce and divide among individual serving bowls. Spoon a little of the remaining sauce over each serving and sprinkle on the cheese, if you like.