Though classically made sans onions, a Roman affectation, the key to this dish, what separates it from all the others is the use of Guanciale. Guanciale is cured porcine cheek, as opposed to Smoked Pork Belly (American Bacon), Dry Cured Pork Shoulder (Hot Coppa), or Dry Cured unsmoked Pork Belly (Pancetta). And while all the meats listed can be used as substituted in a pinch, they are mere shadows of the real thing. Guanciale has a much more intense flavor so a little goes a looooooong way. It also lends almost a "Creamy" texture to the dish.
Sadly, I was forced to use Hot Coppa this time... I thought I still had some Guanciale in the refrigerator. Alas, much to my dismay and forgetfulness, I did not. Angels wept, as did I. But since I already set my teeth on having all'Amatriciana for dinner I went ahead and substituted.
Traditionally, at least in Amatrice, this "Sugo" (sauce) is served over Spaghetti; while in Rome, Bucatini is the preferred pasta vehicle. Me? I am a Spaghetti kind of guy... But, in Roman fashion, I like a little onion in mine as well.
1/4 cup Onion, chopped
1/2 tsp Red Pepper Flake
4 oz Guanciale (though I used Hot Coppa this time)
1/2 cup White Wine
15.5 oz can Diced San Marzano Tomatoes
1/2 cup Pasta Water
1/3 cup Pecorino Romano, freshly grated
Before draining the pasta, reserve 1/2 cup of the starchy pasta water and set aside.