In this wonderfully simple and satisfying dish, the ricotta takes on the flavor of the pancetta and coats the pasta with a delicious creaminess. The parsley is mixed in at the end, its raw flavor adding freshness to the sauce.
Fill a pot for the pasta with about 6 quarts of water, place over high heat, and bring to a boil.
Peel the onion and finely chop it. Put the butter in a 10-inch skillet and place over medium-high heat. As soon as the butter has melted, add the onion. Sauté until the onion turns a rich golden color, about 5 minutes.