I'm always asked the question "What is my favorite Roman dish?" Impossible to answer. But forced to name my favorite Roman pasta, on most days, my answer would be rigatoni all'amatriciana.
The official pasta for amatriciana is bucatini, but since that long hollow noodle has a way of ending up in your hair and on your clothes, rigatoni is often preferred.
This dish originated in the town of Amatrice in Northern Lazio and didn't include tomatoes until the Romans seized it and claimed it for their own Serious food fights have been known to occur over whether or not onions should be included in the recipe (most Romans seem to like it this way but many purists do not) and whether pancetta (Italian bacon) or guanciale (similar but from the jowl of the pig and covered with black pepper) should be used.