Another great day/evening meal trip form Lisbon is to go to Almeirim (take the A1 highway to Santarém, and it's just across the river). Almeirim is famous for its sopa da pedra, a traditional soup that evolved from the old "stone soup" legend (and sure enough, in most restaurants, each serving of soup comes with its own polished stone in the bottom of the bowl). It's a hearty, red-bean based soup fortified with potatoes and the usual suspects--chouriço, morcela, and bacon. The best place in town to sample this is the restaurant O Toucinho.
The other specialty here is grilled meats (which they do over charcoal), of which the best is a sort of thick lamb chop, but cut in a way I have never seen anywhere else, the name of which I can't for the life of me remember. Just ask which it is--it's the most popular one and, unfortunately, they're often out of it (a bit of Googling produced the word "rinzada"... I think that may be it, but do some inquiring to be sure). The bread is also spectacularly delicious here, fresh from the oven. The restaurant is a bit tricky to find if you don't know where you're going. Just head for the bull ring, then ask someone for directions. Closed Thursdays.
Restaurante O Toucinho
Rua de Timor, 20
2080-103 Almeirim, Portugal
(+351) 24 359 22 37