In the meantime put a tablespoon of olive oil in a pan, heat it up and then add the pancetta. Cook until it browns, stirring from time to time.
Take the pancetta out of the pan and keep it aside. Add the onion to the pan with the grease of the pancetta and cook until brown. Add the chopped tomatoes, the chopped chilli and cook for 10 minutes. Then add the pancetta to the sauce and the remaining olive oil.
Cook the pasta in the boiling water till al dente. Drain and then add it to the pan with the tomatoes and the pancetta. Cook it for another minute stirring it all well so the pasta will absorb the sauce. Serve with the grated Pecorino cheese.
You can use 400g of fresh tomatoes instead of tinned.