Put the steak in a shallow dish and sprinkle with the shallots, vinegar, oil, sea salt and ground black pepper. Rub over the meat with your hands. Leave for at least a hour, or overnight in the fridge.
Heat a griddle pan or barbecue. Cook the steaks for 3-4 mins on each side until well browned.
Transfer to a board, cover with foil and rest for 5 mins. Serve thinly sliced with new potatoes and salad, or in tortillas, with lettuce, avocado and soured cream.