- 1 1/2 cup red wine
- 1/4 cup light brown sugar
- 8-10 cloves garlic, smashed
- 2 medium red onions, peeled and cut into thick slices
- 1/4 cup olive or vegetable oil
- 1 tablespoon all-purpose flour
- one 6- to 7-pound prime rib roast
- kosher salt and freshly ground black pepper, for seasoning
- 6-8 sprigs fresh rosemary
- Mix together the red wine, sugar, garlic, onions, and oil and whisk. Stir well until it is all dissolved.
- Pour the marinade over the top of the roast, cover, and store chilled for a minimum of 12 hours, and up to 36 hours.
- Remove the roast from refrigerator 1-2 hours before roasting to allow it to come to room temperature. Preheat oven to 375 degrees. Put 1 tablespoon of flour into the oven bag, shake, and then place bag into large roasting pan.
- Remove the roast and onions from marinade. Season the roast with salt and pepper. Lay the rosemary sprigs on top of the roast and tie them on using a kitchen twine.
- Put the onions in the middle of the roasting bag and place the beef onto the onions. Insert an instant-read thermometer into meat. Seal the bag and put the roast into the oven. Roast for 1 hour 45 minutes, or until the beef reaches an internal temperature of 135 degrees, which is medium-rare; if you want well-done, leave until desired temperature is reached.
- Remove the roast from the oven and allow to rest 15-20 minutes before carving. Carve slices across grain of meat, and serve with roasted onions.