In Bairro Alto there are several Fado Evening shows, all together, but after having seen all of them, my recommendation is Cafe Luso. You can get there through the famous Elevador da Gloria.
You can just pay a drink and watch fado, or have a dinner at the same time that the show. Show with two drinks will cost about 20 euro. With dinner is about 35 euro. The shows never finish until 1 AM. You can enter at 8 PM, for instance, and seat until 1 AM. Apart from fado songs there are folkloric shows with the public participation.
Travessa da Queimada 10 (Bairro Alto) Lisbon Lisboa Portugal