Very very small restaurant, but great food:
must have the "Bacalhau Ti Natércia". It's codfish and vegetables rolled in puff pastry and cooked in the oven. The owner is very nice and chatty (even tought I doubt she can speak much english;-).
At the end of the meal you wont believe how cheap that is.
You might want to call if you plan to go there with friends because the place is really small.