Take the steak out of the fridge and allow it to come to room temperature for about 30 minutes, which helps it cook evenly. Dry the steak with paper towels before seasoning.

While the steak comes to room temperature, make the chimichurri. Add the parsley, garlic, olive oil, red wine vinegar, lemon juice, red onion, red pepper flakes, oregano, salt, and pepper to a food processor. Pulse until combined, scraping down the sides as needed. Stop when the texture is slightly chunky, not fully pureed. Taste and adjust seasoning if desired, then set aside.

Preheat a cast iron grill pan over medium-high heat for about 5 minutes. Brush the steak with olive oil, then season on both sides with the salt and pepper.

Once the pan is hot, place the steak on the grill pan. Cook for about 4-5 minutes per side for medium-rare, adjusting the time for your preferred doneness (see notes for a doneness guide).

Use an instant-read thermometer to check the steak’s internal temperature. For medium-rare, aim for 130°F; for medium, 135°F; and for medium-well, 145°F.

When the steak reaches your desired temperature, remove it from the grill pan and transfer it to a cutting board. Cover it loosely with foil and allow it to rest for at least 5 minutes to lock in the juices.

Slice the steak thinly against the grain. Drizzle with the prepared chimichurri, saving some for dipping.

Serve warm and enjoy!