The restaurants along or near Rua 31 de Janeiro may have river views, but they don't necessarily serve the best food. This friendly, ham-and-garlic-bedecked place—behind a service station off a square at the end of the main street—has no views, but the regional fare served on its wooden tables is fantastic. Regular dishes include cozido à portuguesa (a meat, bean, sausage, and vegetable stew), cabrito assado (roast kid) and tripas (tripe and beans).
On weekends there's arroz de cabidela: chicken and rice in a rich gravy made from the animal's blood. If you're planning on having dinner, come around 7 pm, because it gets packed.
Rua da Olivença, Amarante, 4600-096, Portugal