Restaurants in Porto and Lisbon

https://www.facebook.com/Santelmo-Restaurante-Café-988214471233446/
Santelmo in the Bairro Alto. Small place, great prices, and one of the best fish dishes I've ever had (Sea Bream)! Great tray of free apps.

Don't miss Bonjardim for the piri piri chicken in Lisbon--excellent and reasonably priced. It has a four star rating.

My experiences - https://www.yelp.com/collection/c4DDuTqoI-3WsEeUfcSH8A

In Lisbon, try the Time Out market - lots of the city’s best restaurants have stalls where they cook a limited menu of specials - including great seafood. Big tables in the middle of the market to eat at.

I agree with the recommendation for Timeout Market .Mercado da Ribeira is the real name I think, but they seem to promote the Timeout name. It is right on the entrance.
Lots of fun with pick and mix- Thai, Portuguese cuisines, wines, desserts, the omnipresent natas....
The only issue to be aware of is that the tables are communal, are not cleared or cleaned efficiently, and many diners leave their trays and cups on the table when they leave. So a little messy when crowded.
My spouse wanted to go back every day while we were there!

I recommend Cervejaria Ramiro in Lisbon for delicious fresh seafood. Recommended by the late Anthony Bourdain.

O Palacio is a great seafood restaurant in Lisboa. Its on Rua Prior do Crato. It was on a culinary tour we took from Culinarybackstreets. They have short pieces on various restaurants in Lisbon and Porto. We use them all over the world. Another favorite of mine is O Pitieu da Graça. Planning on returning there for the 3ed time when I’m in Lisboa next month.

Porto residents head north to the fishing suburb of Matosinhos for their fresh fish restaurants. My favorite is Tito II but there are many others to choose which are great as well. Getting there is easy by metro or bus. The #500 bus leaves directly across from the Imperial McDonalds, paralleling the Atlantic Ocean, mine was a double decker, ends at Matosinhos. Metro is quicker, from Trinidad in the direction of Senhor de Matosinhos until the end. Uber as well. Well worth the time for price and assurance of fresh fish. You may also get to see surfers if you head to the beach too.

Two visits last year and heading back in September. Porto #1 for me followed by Lisbon. Enjoy!

What Pab says concerning Porto is absolutely true. We head North to Matosinhos for seafood and for fresh grilled fish.

Besides those transports mentioned above, you also have bus 501, from/to Matosinhos beach/Av. dos Aliados (goes inside the city, not by the sea/river - for this is 500 as said).

My favourites for seafood: Lusíadas, Marisqueira A Antiga, O Marujo, Májara. Etc. A litlle bit further north, across de river - you can take bus 500, leave at last stop "Mercado de Matosinhos", walk through the bridge towards Leça da Palmeira village, and 1km more or less after the bridge turning left, you find lots of restaurants, one is also very good for seafood, named "Casarão do Castelo" - that's where the football players (and the other members of the team) from Futebol Clube do Porto often go.

Besides the mentioned, at Rua Heróis de França you can find a lot of very good restaurants for grilled fish. They grill the fish outside, in the street, so just take a look and choose the one that appeals more to you. The same at Av. Serpa Pinto, lots of good restaurants., and in the streets connecting one street to the other.

All the mentioned places also have meat dishes, in case you are with someone that does not want fish or seafood.