Ingredient:
3.5 kg (6 ½ lb) prime rib of beef on the bone
Vegetable oil, brushing
Salt and black pepper
1 onion, quartered

To serve:
Yorkshire puddings
Gravy of your choice
Horseradish sauce

Method:
Insert a meat thermometer, if using, into the middle of the meat. Put the beef into a roasting tin, brush all over the meat with oil, and season with salt and pepper. Add the onion quarters to the tin and roast with the beef in a preheated oven at 200℃ (180℃ fan, Gas 6) for 20 minutes.

Meanwhile, make the Yorkshire pudding batter and set aside.
After the beef has been roasting for 20 minutes, baste it with the juices from the tin, and lower the oven temperature to 180℃ (160℃ fan, Gas 4).

Roast, basting frequently, for a further 1 ½ hours for rare beef, 1 ¾ hours for medium, and 2 hours for well-done, or until the meat thermometer registers 60 ℃ (140F), 70℃ (160F), or 80℃ (175F).

Transfer the beef to a carving board, cover with foil, and leave to stand in a warm place. Increase the oven temperature to 220℃ (200℃ fan, Gas 7) and bake the Yorkshire puddings.

While the puddings are in the oven and the meat is resting, make the gravy in the roasting tin according to the instructions on.

Serve the beef with the Yorkshire puddings, gravy, and horseradish sauce.