Enma
Expensive, but good
In the Boavista area, this restaurant at the Sheraton hotel, offers fine, modern cuisine for lunch and dinner. Dinners are a la carte, and there's a tasting menu depending on the time of year. The prices are quite high for Porto, although Portugal is cheaper than many other European countries. You can certainly have a cheaper meal elsewhere in the city, but I don't think you can have a better one.
+6