Cook the pancetta over medium heat in a large pan until crisp and golden.
Use a slotted spoon and remove the pork from the pan and set aside.
Cook the onion, garlic and chilli flakes in the pork fat until softened and fragrant.
Pour the tomatoes into the pan and season with salt and pepper. Add the pancetta back into the sauce and simmer for 5-7 minutes until the sauce has reduced slightly.
Cook the pasta in a large pot of salted water. Reserve 1 cup of cooking water and drain.
Toss the pasta with the sauce and add a splash of cooking water.
Serve the pasta with a generous amount of grated Pecorino Romano.