2) Press the pepper and salt into the steak with the palm of a hand. Transfer the steaks to a baking dish and place in the refrigerator. Leave to marinate for 4 to 8 hours.
3) Add the extra-virgin olive oil to a medium saucepan over a medium heat, add the onions and lightly saute until the onions are caramelized. Add the garlic and cook until garlic begins to turn brown.
4) Deglaze the pan with the wine and balsamic vinegar. Add the sugar and leave to simmer and reduce for 20 to 30 minutes until mixture reduces to 180ml.
5) Place the steaks over a hot grill. Cook for 5 minutes, moving once on the first side to mark the steaks with crossed lines. Flip and cook for 4 minutes on the other side, again only moving once to mark the steak.
6) When the desired doneness is achieved, remove the steaks from the grill and leave to rest for 3 to 4 minutes. Meanwhile, strain the wine mixture and return to the heat to reduce for 5 more minutes or until a thick syrup is created. Serve with the steaks.