Steps

Add guanciale in a cold pan on medium heat to allow the fat to render and cook until golden brown

while the fat is rendering, bring a pot of salted water a boil and cook the bucatini till al dente. We don't want to use too much water because we want starchy pasta water for your sauce. Lightly salt the water to avoid making the sauce too salty since pecorino is already salty

Once the guanciale is golden brown, add a pinch add red pepper flakes if you like a bit of heat

Add tomatoes to the pan and crush them and bring to a simmer to allow the sauce to thicken. Season with salt as needed

once the bucatini is al dente, mix with the tomato sauce along with some of the starchy pasta water

add the pecorino and toss

garnish with additional pecorino if you want