Start with a rump cap. You may have to tell your butcher to do their homework. They call it top sirloin in an American churrascaria. They are 2 to 3.5 pounds each, they have a nice layer of fat on the outside, and they are delicious.
Score the picanha in a diamond shaped pattern. That allows the fat to cook thoroughly
Flip it over to see which way the grain goes. In this picture, you can see that the grain goes left to right, and slightly up on the right.
Cut the picanha into three or four strips against the grain.
Skewer the pieces, folding over with the fat cap exposed, in any arrangement you like. I chose two per skewer. Sprinkle thoroughly with rock salt on both sides.
Broil in oven, flipping every two minutes, until brown on the outside, about 10 minutes. Remove from broiler and let rest for at least 3 minutes. Slice off ends and serve.
Re-salt and repeat cooking/serving process until it’s all gone.