We visited here in late October 2014 a couple of times. They serve canteen-style food, where you select a number of items for a fixed price.
The food was good, portions were generous, and very filling. When we went, they offered some seitan dish, some lentil dish, and salads. Desserts were limited but also good.
The place lacks charm, being more of a functional seating are in set-up than a cosy retreat. There isn't loads of room, but there was always space for us to sit and enjoy our food without the feeling that we were rushed.
Water is available from a cooler.
It's located close to Praça do Comércio.
Recommended. Would visit again if in the area.
Cons: Lacks ambience