Let us first get the confusion out of the way: there are 2 places called Café Buenos Aires. They are within 20 metres from each other. The owners are the same and the menu is too. Both are excellent. I used to go quite often to the original one (located on the corner with a small terrace). Its main pitfall was its lack of space and the difficulty to get a table. Fortunately the second one has fixed these problems and that is why I am writing about it.
The Café Buenos Aires na Fábrica (literally “in the factory” since it is located in an old pastry factory) is a nice and cozy restaurant that has the feel of a Parisian Grand Café. The menu is a mix of excellent Argentinian steaks and original salads and starters. It is all very good and tasty. Ask some starters to share with your companions, such as the hummus, endive and gorgonzola or empanadas.
This is a great place to start a lively night out (walking distance from Bairro Alto) or to have an intimate dinner with friends.
The only downside is the fact that they do not accept cards, so cash is king. Better make a reservation.