Photograph: Dan Jones
For the chimichurri sauce, whiz all the ingredients with some seasoning in a mini food processor until finely chopped, adding the cumin to taste.
Light the barbecue or preheat a griddle pan. Brush the steaks all over with olive oil and season on both sides with salt, pepper and ground cumin. Barbecue or griddle the steaks for 2-3 minutes on each side or until cooked to your liking. Set aside to rest for 10 minutes, then serve with the chimichurri sauce.
Get ahead: make the chimichurri sauce a few hours ahead.
Kitchen secret: either cook one steak per person or, to make them go further, thinly slice the steaks and serve in tortilla wraps with the sauce and soured cream.