I wholeheartedly agree with Swissaire here: Bassi is the best meat (beef) restaurant in Brazil. You won't have the huge amounts served at the churrascarias , but the quality of the beef served there is way, way better.

Caveats: it's in São Paulo, not Rio; it's expensive and, as I said, the portions are not huge. But definitely worth it.

Bassi published a DVD a while ago with lots of information about meat. Some parts of this DVD are avaiable at YouTube, as Swissaire said. The following segment shows him "working" the whole contra-filé, and carving the rib-eye (he calls it "olho de bife", in a free translation from argentinian beef-speak), at 6:15 in the video:

http://www.youtube.com/watch?v=bwHzpOy3rRM