Chop guanciale into strips or pieces. Place the guanciale in the saucepan and bring to medium heat. Fry for about 8 minutes or until the fat renders and the guanciale is golden brown. Remove from the pan, leaving at least 3 tablespoon of oil.
Hand-squeeze the peeled tomatoes into the sauce. Ground fresh pepper into the sauce. Bring to a boil and then lower the heat to a simmer.
Bring a large pot of water to a boil. Salt the water and add the bucatini. Cook until 1-2 minutes before al dente. Save pasta water for the sauce.
Add ¼ cup of pasta water into the sauce and mix well. Drop in the bucatini and toss in the sauce. Let it simmer for 2 minutes.
Add pecorino romano to the sauce and toss to combine. Serve immediately, adding the crispy guanciale on top of the pasta.
Notes
Always cook guanciale starting in a cold pan to render the fat and make the meat golden-brown and crispy.
When simmering the sauce keep the pan at a high enough temperature to keep a strong simmer. Bring the sauce back to a simmer after you add the pasta water.