Light grill and set up for rotisserie cooking. I'm using an infrared rotisserie burner but charcoal can be used as well. Allow the grill to preheat.
While the grill is preheating, trim off any silver skin from the meat side of the picanha. Then, slice the picanha (with the grain of the meat) into three of four individual pieces that are about two inches wide.
Shape each piece into a semicircle, with the thick fat layer on the outside of the circle.
Skewer the picanha onto the rotisserie spit. Secure the meat in place with the rotisserie forks and rub the meat with olive oil. Then, season with kosher salt.
Place rotisserie on the grill, turn on the rotisserie motor and allow the meat to roast for about 15 minutes, or until a nice char and color has been achieved.
Remove the meat from grill, and slice outside layer directly from spit and serve with chimichurri. Return the spit to the grill so the uncooked picanha can roast. Repeat the process until finished.