Preparation

• Take the beef out of the refrigerator 2 hours before cooking so it can come to room temperature. After 30 minutes, season the meat on all sides with the fleur de sel and cracked black pepper.
• Position a rack in the center of the oven and heat oven to 325ºF.
• Turn on the exhaust fan. Heat a 12-inch skillet over high heat for 1 minute. Swirl in the olive oil and,  when the oil puts off its first wisp of smoke, place the beef in the pan, and sear it on all the outer sides (not the cut sides) until well browned, 6 to 8 minutes total. Use a set of tongs to flip the beef; be careful of splattering oil. With two sets of tongs, transfer the beef, bone side down, to a roasting rack set in a small roasting pan. Arrange the rosemary, thyme, garlic, and butter evenly on top.
  
• Roast the beef, basting every 30 minutes with a bulb baster, until a thermometer inserted into the center reads 120º to 125ºF for rare, about 2 hours. Cook to 130º to 135ºF for medium-rare (about 2-1/4 hours), 140º to 145ºF for medium (about 2-1/2 hours). Let the meat rest at least 15 minutes before carving.

For a delicious sandwich using the leftovers see Prime Rib Sandwich with Roasted-Garlic Dijonnaise.