Marinate the steak fillets for 30 minutes in olive oil with a generous amount of salt and pepper (you should be able to see the coating of salt and pepper) and set aside to allow the meat to come to room temperature.
Meanwhile, finely chop the produce (a food processor helps a lot).
Add the liquid and salt (adding more if needed), and refrigerate the sauce.
Place the steaks on the grill for 4-5 minutes per side.
Cut the steak into strips and serve with the chimichurri sauce.