For the sauce in a large skillet add the olive oil and heat over medium high. Add the pancetta and cook for 6 minutes. Remove the pancetta from the oil and let sit while you continue cooking. Add the onion and cook for 5 minutes and then add the garlic, tomatoes, salt, pepper and the cooked pancetta. Simmer, uncovered, over low heat until the sauce thickens, which should take about 15-20 minutes. Stir in the cheese at the end.