Picanha is considered the best cut of beef in Brazil. It is the rump cap, which has a thick layer of fat covering the meat — this slowly melts (or renders down) when cooked slowly over indirect heat, adding flavour to the meat and keeping it moist and tender. Traditionally, the rump cap is sliced into thick steaks, threaded onto sword-like skewers and cooked on a rotisserie. If you can’t find the right kind of skewers (these can be purchased online) you can cook the steaks individually on a barbecue chargrill.
Picanha is not a common cut, so you’ll need to ask your butcher to specially cut the rump cap for you. You may still have to buy the other parts of the rump too, but these can be frozen and used another day.