Preparation

Make the sauce

• Combine the cilantro, parsley, oregano, and garlic in a food processor and pulse until finely chopped. Scrape the mixture into a bowl and stir in the olive oil, vinegar, lime juice, red pepper flakes, and 1/2 tsp. salt.

Cook the steak

• In a flat dish or shallow bowl, combine the crushed peppercorns with 2 tsp. salt. Firmly press both sides of the steaks into the mixture so they’re well coated. Set aside to come to room temperature, at least 20 minutes and up to 45 minutes.
• Position a rack in the center of the oven and heat the oven to 350°F.
• Heat a 12-inch cast-iron skillet over medium-high heat until very hot, about 2 minutes. Add the oil, swirling the pan to coat the bottom; then add the steaks and cook, undisturbed, until nicely browned on the bottom, about 4 minutes. Flip and cook, undisturbed, until nicely browned on the other side, about 4 minutes. Transfer the skillet to the oven and cook until an instant-read thermometer registers 120° to 125°F for rare, 130° to 135°F for medium rare, or 140° to 145°F for medium, 2 to 7 minutes. Let the steaks rest on a plate, loosely covered with foil, for 5 minutes. Serve the steaks topped with the chimichurri sauce.