Chumley'S Prime Rib - cooking recipe

Ingredients

fresh ground black pepper (to taste)
garlic powder (to taste)
1 tablespoon dark soy sauce
1 1/2 tablespoons Kitchen Bouquet
1 tablespoon Coleman's dry mustard
8 -9 lbs beef rib roast, bone in
1 cup peeled an sliced yellow onion (1/8 inch thick)

Preparation

Preheat the oven to 450 degrees.
Rub the seasonings on the roast in the order listed.
Place the roast on a rack, fat side up in a roasting pan. Pack the onions on the roast.
Roast in a 450 degree oven for 20 minutes.
Reduce the oven temperature to 325 degrees and roast 1 hour.
Reduce the temperature again to 300 degrees and roast about 1 hour more. Cook the roast at this temperature until it is done to your liking. The recipe says 115 degrees for rare in the center with a meat thermometer. I go to about 135, that is a pretty good medium.
Remove the roast from the oven and allow it to stand for 15 minutes in a warm place.
Slice and serve immediately.