Preheat the oven to 375°F.
Bring the picanha steak to room temperature.
In a medium bowl, whisk together the Chimichurri Seasoning, olive oil and white wine vinegar. Set aside half of the mixture (as a sauce for serving) then rub the remaining mixture all over the picanha.
Place a large oven-safe cast-iron or stainless steel skillet over medium low heat. Add the picanha steak, fat cap side down, and cook until a majority of the fat has rendered.
Transfer the skillet to the oven and roast the picanha steak until it reaches your desired temperature. (Timing will depend on the thickness of your cut, but roughly 30 minutes for medium-rare.)
Remove the picanha steak from the oven and let it rest for 10 minutes before slicing against the grain and serving with the reserved chimichurri sauce.