Stand the beef, fat side up, in a roasting pan. Season with salt and pepper. Insert a meat thermometer into the centre of the meat, making sure the tip does not touch the bone. Roast the beef, uncovered, in a 230 degrees C. Oven for 15 minutes. Reduce the heat to 180 degrees C. And continue cooking, allowing a total cooking time of 36 minutes to the kilo for rare beef [ internal meat thermometer reading 60 degrees C]. Allow 44 minutes to the kilo for medium beef [internal temperature 70 degrees C]. Allow 56 to 60 minutes to the kilo for well done beef [internal temperature 80 degrees C]. Remove the beef from the oven. Cover with aluminium foil and let it stand for 15 minutes to allow the juices to return to the centre of the beef.