Prepare the steak: Set the steaks on a cutting board and slice them in half crosswise. Using your knife, round out the clean-cut edges so the sides look softer. Use paper towels to pat the steaks dry, then season all over with 1 teaspoon salt and 1/2 teaspoon pepper. Set aside 15 to 30 minutes to bring to room temperature.
Meanwhile, make the chimichurri sauce: Place the cilantro, parsley, onion, lemon juice, vinegar, garlic, red pepper flakes, 1 teaspoon salt and 1/4 teaspoon pepper in the bowl of a food processor and pulse until roughly chopped. Slowly pour in the olive oil and process until the chimichurri is semi-smooth, about 4 seconds. Transfer to a small bowl and set aside.
Heat a grill or grill pan over medium-high heat. Brush both sides of each steak with the vegetable oil, then cook, undisturbed, until marked, 3 to 5 minutes. Flip and cook until a thermometer registers 125 degrees F for medium rare, 3 to 5 more minutes. Transfer to plates and let rest 5 minutes. Serve with the chimichurri sauce.
Photograph by Paul Sirisalee
Recipe courtesy Melissa d'Arabian for Food Network Magazine