||Brush each sirloin steak lightly with oil. Season with salt and pepper. Combine the sliced sweet potato with cumin and oil. Preheat the char-grill pan to moderately-hot, add the sweet potato, and cook each side for a few minutes until tender. Remove sweet potato and set aside.
||Reheat the char-grill pan to hot before adding the meat. Cook on one side until the first sign of moisture appears. Turn steaks once only. Test the steaks for degree of doneness with tongs. Rare is soft, medium feels springy and well done is very firm.
||Remove steaks from heat, loosely cover with foil and rest steaks for 2 minutes before serving. Place sweet potatoes on the serving plates, top with steak and spoon on a little tomato relish, serve with a green salad.