Osteria der Belli
You might overlook Osteria der Belli because of its proximity to the central square of Trastevere, Piazza Santa Maria in Trastevere—and that would be a crying shame. Leo, the owner, is Sardinian and has been running this place daily for over 35 years, and, while Roman dishes are on the menu, it excels at seafood and Sardinian cuisine. Between the friendly service and quality food, this one's a real find in an otherwise-touristy part of Trastevere.