Juicy, tender prime rib roast and delicious gravy.
- 1 (4.5 pound) beef prime rib roast at room temperature
- coarse sea salt, or as needed
- freshly ground black pepper, or as needed
- 1 onion, quartered
- 1/4 cup unsalted butter
- 1/4 cup all-purpose flour
- 1/4 cup red wine
- 1 (32 ounce) carton beef stock
- 4 sprigs fresh thyme
- Preheat oven to 275 degrees F (135 degrees C).
- Rub beef roast with sea salt and black pepper. Heat a large cast-iron skillet over medium-high heat; sear roast on all sides in the hot skillet, 2 to 3 minutes per side. Turn roast so the ribs and fat side are facing up.
- Roast prime rib in the preheated oven for 45 minutes; scatter onion quarters around roast and continue cooking until an instant-read meat thermometer inserted into the thickest part of the meat reads 130 degrees F (54 degrees C) for rare, about 2 more hours.
- Remove roast from skillet, wrap meat in aluminum foil, and let rest for 15 to 20 minutes to let juices reabsorb into the meat. Leave onion pieces in skillet.
- Pour drippings from skillet into a bowl and skim off excess grease. Return degreased drippings to skillet with onion pieces, place over medium heat, and melt butter in the drippings. Whisk flour into mixture to make a paste, 1 to 2 minutes. Stir red wine into flour paste until smooth. Mix beef stock into pan gravy until smooth; stir thyme sprigs into gravy.
- Reduce heat to low and simmer gravy until thickened, 5 to 8 minutes. Strain gravy, discard onion pieces and thyme, and serve with prime rib.