Portinha is several steps up from most per-kilo restaurants you'll find. There is a plethora of meat and seafood dishes on offer, most of which are inspired by traditional Bahian cuisine and taste like they were made to order in an upscale bistro. It's located on a pleasant patio in the Shopping d'Ajuda complex.
At the time of writing there was a buffet-livre (all-you-can-eat) option every Thursday for R$29.