Portuguese cuisine is now more and more sophisticated and you can also find in some restaurants amounts to versions of home or country cooking, often using fresh herbs and spices - but the food is much better than in southern Portugal and portions are extremely generous (you can ask for a "meia dose", or half-portion).
Note, however, that you will be charged for what might appear to be freebies plonked on your table, such as bread, olives and charcuterie.
If you don't want them, send them back, or simply don't eat them. But eating out is relatively cheap in Portugal.
Fish and seafood are a mainstay, including the ubiquitous bacalhau (dried salt cod), which supposedly has enough recipes for every day of the year.
Meat is just as popular: game, beef and goat, and in particular pork: spit-roasted suckling pig is a favorite. And offal is ubiquitous on menus.
Porto specializes in stewed tripe, cooked with haricot beans. Indeed the nickname for the locals is "tripeiros" (tripe eaters), supposedly because available meat was given to sailors, leaving only tripe to eat in the city.
Portuguese menus often feature soups, including te filling bread soups, açordas. Brazilian dishes, and a number of Brazilian restaurants, also feature.
Culture of Porto city (http://photoblog-favoritus.blogspot.pt/2014/12/culture-of-porto-city-en.html)