Taxi drivers have their pick of the land and where they eat the food is often as authentic as you'll find.
Here is a great place named Divers' Club. It sells well-known food such as braised pork on rice and chicken rice. If you have problems finding the place, ask a taxi driver, they all know where it's at.
Just the corner of NK Hostel, less than 30 seconds by walking
OPENS: Monday to Friday 11:30–13:00, 17:30–04:30 (Closed on Sunday)
ADDRESS: No. 399-2, Section 5, Nanjing East Road, Songshan District, Taipei City, 105