Blend parsley, cilantro, green onion, garlic, avocado oil, red wine vinegar, lemon juice, and salt in a small food processor.* You may need to scrape the sides and pulse a few times.
2 cups parsley, 1 cup cilantro, 1 green onion, 3 garlic cloves, ½ cup avocado oil, 2 tablespoon red wine vinegar, 1 tablespoon lemon juice, 1 teaspoon salt
Add about ½ to ¾ of the sauce to a large plastic bag or shallow glass dish with the flank steak. Marinate for 30 minutes to 24 hours. ***
2 lbs flank steak
Heat a cast iron pan on medium-high heat. Sear steak on each side for 4-6 minutes. Discard leftover marinade. Slice steak and top with leftover chimichurri sauce.
Notes
*If your food processor is a 7-11 cup version, you need to make a double batch of this sauce for it to blend right. This is ideal anyways. You can use all the herbs you bought and freeze some for next time.*Nutrition facts vary since ¾ of the marinade is discarded.