Peel, halve, and seed the tomatoes, then cut into thin strips. Cut the guanciale into small pieces, put in a skillet with the oil, and sauté for 2 to 3 minutes, or until crisp. Remove the guanciale with a slotted spoon to a bowl and keep warm. Reserve the contents of the pan.
Chop the onion and put it in a saucepan with the chile and the contents of the guanciale pa