Prime Rib and Potatoes

Using sharp knife, trim roast’s fat cap to even 1/4-inch-thickness; reserve and refrigerate trimmings. Cut 1-inch crosshatch pattern in fat cap, being careful not to cut into meat. Rub 2 tablespoons salt over entire roast and into crosshatch. Transfer to large plate and refrigerate, uncovered, for at least 24 hours or up to 4 days.

Adjust oven rack to lower-middle position and heat oven to 250 degrees. Cut reserved trimmings into 1/2-inch pieces. Place 4 ounces (about 1 cup) of trimmings in rimmed baking sheet, then set wire rack in sheet. Season roast with pepper and place, fat side up, on wire rack.

Roast until meat registers 115 degrees for rare, 120 degrees for medium-rare, or 125 degrees for medium, 3 to 3 1/2 hours. Transfer roast to carving board, tent with aluminum foil, and let rest for 1 hour. Carefully remove wire rack and reserve beef fat in baking sheet (there should be about 1/2 cup; if not, supplement with vegetable oil).

Increase oven temperature to 450 degrees. Microwave potatoes, covered, in large bowl until they begin to release moisture and surfaces look wet, about
 7 minutes. Pat potatoes dry with paper towels. Toss potatoes with rosemary, 2 teaspoons salt, and 1/2 teaspoon pepper. Transfer potatoes to baking sheet and carefully toss with reserved fat (fat may be hot). Roast until tender and browned, 35 to 40 minutes, redistributing halfway through cooking. Season potatoes with salt and pepper to taste.

Pat roast dry with paper towels. Heat oil in 12-inch skillet over medium-high heat until just smoking. Sear all sides until browned, 6 to 8 minutes total. Transfer roast to carving board. Carve meat from bones and cut into 3/4-inch-thick slices. Serve with potatoes.