1. Heat the oil in a large saucepan over medium heat. Add the onion and cook, stirring, for 3 minutes, or until softened. Add the pancetta and continue cooking, stirring often, for 5 minutes, or until the pancetta is lightly browned.

2. Add the wine and cook about 5 minutes, or until it evaporates by half. Stir in the tomatoes and their juices, reduce the heat to low, and simmer briskly for 15 minutes, or until thickened. Season with salt and red pepper flakes.

3. Meanwhile, bring a large pan of salted water to a boil over high heat. Stir in the spaghetti, and cook according to the package instructions, or until the pasta is al dente. Drain the spaghetti well. Add to the sauce and stir well. Remove from the heat and stir in the cheese. Serve hot, with additional cheese passed on the side.