Bucatini all'Amatriciana

Set the pasta water to heat, salt it when it boils, and cook the pasta. While this is happening, heat the oil in a skillet, add the diced meat, and cook until it browns, stirring the pieces about. Remove them to a sheet of absorbent paper with a slotted spoon and keep them warm. Add the onion to the grease in the pan, together with the hot pepper, and when it begins to color add the tomato pieces, which should be well drained. Cook, stirring, for 5-6 minutes, then return the diced pancetta to the pot and heat it through. Drain the pasta while it's still a little al dente, turn it into the skillet with the sauce, cook a minute more more, stirring the pasta to coat the strands, and serve, with grated pecorino.

Notes:
First, Italians traditionally make Amatriciana sauce with Guanciale, salt-cured pork jowl. It is similar to flat pancetta, but not as lean, and therefore has a richer, more voluptuous feel to it. If you can find guanciale, by all means use it, though in its absence pancetta will work. Bacon is not a good substitute, because it is smoked and also contains sugar not present in either pancetta or guanciale.
Second, Amatriciana sauce derives from a much older sauce called La Gricia, which the shepherds used to make by sautéing diced guanciale so gently as to keep it from browning, and adding freshly boiled pasta, a healthy dusting of pepper, and grated pecorino Romano. The Amatriciana sauce, with tomatoes, was initially enjoyed by the nobility, because only they could afford tomatoes.