Make the chimichurri by combining parsley, oregano, garlic, shallot, and red pepper flakes in a bowl. Add the red wine vinegar and olive oil, season with salt and pepper, and stir to combine. Set aside to rest for at least 30 minutes.

Remove the picanha from the fridge 30 minutes before cooking. Trim the fat cap to approximately 1/4 inch thick, then score it in a crosshatch pattern without cutting into the meat.

Rub the olive oil over the meat side, then season generously with the salt, pepper, and garlic powder mix on all sides.

Slice the roast with the grain into individual steaks roughly 1.5–2 inches thick — you'll get 3–4 steaks from a standard roast.

Preheat your grill to high on one side and medium-low on the other for two-zone cooking. You want the hot side above 450°F.

Sear the steaks over direct heat fat-cap side down first for 2–3 minutes until the fat is golden and rendering. Flip and sear the meat side for 2–3 minutes.

Move steaks to the indirect side and cook until an internal temperature of 130–135°F for medium-rare, approximately 8–12 minutes depending on thickness.

Rest the steaks on a board for 8–10 minutes tented loosely with foil.

Slice each steak thinly against the grain and arrange on a serving board or platter. Spoon chimichurri over generously and serve immediately.