Add all the marinade ingredients (except for the salt and pepper) to a plastic storage bag and seal. Shake to combine ingredients. Add steak and seal again. Place in bowl and them into fridge to marinade for 6-8 hours.
Remove steak from bag and pat dry. Sprinkle with salt and pepper. Add 1 tablespoon of olive oil to a cast iron skillet and place over high heat. Once the oil starts to smoke, add steak to skillet (you may have to cook in batches to accomodate all the steak). Cook for 1 minute or until it turns black. Flip and cook for 1 more minute. Remove from heat. Let cool for 5 minutes and then serve with chimichurri sauce for dipping.
For the chimichurri:
Add all ingredients except for the olive oil into the bowl of a food processor. Pulse until mixture is all chopped up. Scrape down the sides of the bowl if necessary. With the processor on, drizzle in olive oil until it has all been added. Turn off processor. Set aside for after the steak is cooked.