Just another rib roast. This was a 20-pound choice piece of meat. Here are the tips.
Soak it in an onion/salt bath. I took about 6 onions, 1/2 cup of salt, 1 cup of water and blended them into a mash.
I soaked the meat overnight and then pulled it out an hour before cooking.
How long does it take to cook a 20-pound prime rib? I did 30 minutes at the highest heat, then dropped to 275 for 4 hours.