It could be said that bucatini all'amatricana and spaghetti alla carbonara are the 'Romulus and Remus' of Roman cooking. No two dishes typify the local cuisine better than these two yet, like the two founding brothers of the Eternal City, neither actually comes from the city of Rome itself. Bucatini all'amatriciana, as the name suggests, comes from a little town called Amatrice, in the province of Rieti, in what is now north-eastern Lazio. If you look on a map, you'll see that Amatrice is located in a little 'tongue' of Lazio territory that sticks into a mountainous area in the center of the country known as the Gran Sasso (the 'Big Rock'). And, in the old days--before Mussolini changed the borders and most definitely before this dish was invented--it was part of the region of Abruzzo. So, in fact, despite its renown as a Roman dish par excellence, the abruzzesi have a claim to this dish.
In any event, the dish is simplicity itself: while the bucatini are boiling in well salted water, you saute guanciale cut into strips, or pancetta cut into cubes, in a bit of olive oil (or lard) until the pancetta fat is translucent and just beginning to brown slightly. (If you are using guanciale, which is very fatty, you can omit the olive oil altogether.) If you like, you can add a garlic clove along with the pancetta, which you should remove as soon as it begins to color. I also like to add a peperoncino for a little heat, but don't overdo it--this is not meant to be a spicy dish. (If you don't have peperoncino, you can use red pepper flakes, but if you do, add them just moments before the next step, so they don't burn and become bitter.)
Then add very ripe, peeled, seeded and chopped fresh tomatoes. (If you don't good ripe tomatoes on hand, just add good quality chopped or crushed canned tomatoes. (The exact amount of tomato is variable--see Notes below.) Simmer the tomatoes until they have reduced and separated from the fat. Then add a tablespoon or two of grated pecorino cheese, and let it melt into the sauce.
When the bucatini are done--and they should be very al dente--add them to tomato sauce along with another good sprinkling of pecorino cheese and mix well over low heat, allowing the bucatini to absorb the flavors of the cheese and sauce. Serve the bucatini with yet a third sprinkling of pecorino.
NOTES: Like many traditional dishes, l'amatriciana has with many variations. The original bucatini all'amatriciana was entirely in bianco, which is to say it did not contain tomatoes, which became a standard part of the dish only in the 18th century, as tomatoes were becoming a more common part of the central and southern Italian diet. These days it is so common to include tomatoes in the dish that another name is given to the tomato-less version: bucatini alla gricia, after the village of Grisica, not too far from Amatrice. But the amount of tomatoes seems to vary from recipe to recipe. In some versions, amatriciana is a veritable pork-flavored tomato sauce; in other versions, only a bit of tomato--perhaps just a few pomodorini (cherry tomatoes)--are added. So, in short, try adding different amounts of tomato (or none at all) and let your own taste be your guide.
Guanciale, cured pig's cheek, is the original and most authentic ingredient to use. But, of course, guanciale is not so easily found, especially outside Italy. If you can find, by all means use it. Since guanciale is rather fatty, you may not need as much (or any) olive oil. Otherwise, use pancetta and saute it is olive oil (or lard, which will add more 'porky' flavor). The amount of pork to use varies wildly from recipe to recipe, from 125-300g (4-10 oz.) for every 500g (1 lb.) of pasta.
Another variable is whether or not to add garlic, as indicated above, or not to saute along with the pork. I like the savoriness that garlic adds, although some would say that the guanciale or pancetta add enough. Some versions--including almost all non-Italian recipes for dish--call for thinly sliced or chopped onion, but that is definitely not original and, to my mind at least, the sweetness of the onion does not really marry well with the rest of the flavors in the dish. On the other hand, the romanissima Ada Boni does call for onion, in her recipe for amatriciana so, once again, let your own taste be your guide.
Some people like ground black pepper instead, or in addition to, the red pepper.
The type and amount of pecorino is also a matter of some variation. For a truly authentic amatriciana, one should use the local pecorino from the Sabine hills, but that is obviously not an option for anyone outside of Italy (or many in Italy) so pecorino romano is much more commonly used. The technique of adding pecorino three times--once to melt into the sauce, a second time while mixing the pasta with the sauce and a third time on top of the finished dish--comes from the advice in the excellent La cucina romana e del Lazio (Newton & Compton, 1998). Other recipes only call for mixing the pecorino with the pasta, others only using it as a 'topping'.
Some recipes, including the recipe promoted by the 'pro loco' (tourist board) of the town of Amatrice, which can also be found in La cucina romana e del Lazio, call for pouring a bit of white wine to the guanciale or pancetta after they have browned, allowing the wine to evaporate completely. And some recipes also call for removing the pork from the sauce after it has brown, to keep it a bit crispy, and adding back in along the pasta.
One last tip: resist the temptation to salt to the dish too much or at all, especially if you go with the 'thrice-sprinkled' with pecorino method. The salt in the pork, and in the pasta water and in the pecorino should suffice. But, if in doubt, taste and adjust before serving.
Bucatini also go by the Neapolitan name of perciatelli. They look like very thick spaghetti, but have a 'hole' in them. (Hence the name: buco is hole is Italian.) Other pastas can also be made all'amatriciana. In fact, the original dish was apparently spaghetti all'amatriciana, and this is the actual recipe from Amatrice tourist board. Rigatoni all'amatriciana are also quite popular. Fresh egg pastas, on the other hand, don't go particularly well with this rustic sauce.