How to Make It
In a large stainless-steel frying pan, cook the bacon over moderate heat until almost crisp. Remove with a slotted spoon. Pour off all but 1 tablespoon of the fat from the pan.
Reduce the heat to moderately low. Add the onion and cook, stirring occasionally, until soft, about 5 minutes. Add the tomatoes with their juice, the salt, and the pepper and bring to a simmer. Cover and cook for 10 minutes.
In a large pot of boiling, salted water, cook the cavatelli until just done, about 10 minutes. Drain and toss with the sauce, bacon, arugula, and 1/4 cup of the Parmesan. Stir until the arugula just wilts. Sprinkle the remaining Parmesan over the top.
Use 1 1/4 cups watercress or spinach, large stems removed, instead of the arugula. Cavatelli Options
Look for cavatelli in the frozen-foods section of your grocery store. If you prefer, substitute frozen egg noodles or gnocchi in equal amounts for the cavatelli; they have a similar doughy chew. This dish could also be made successfully with spaghetti or, even better, spaghettini.