Preheat oven to 350 degrees F. Combine flour, bouillon powder and black pepper in a shallow pie pan or bowl. Pat roast dry using paper towels. Dredge the roast in the flour mixture, coating thoroughly.
Heat the oil in a large Dutch oven or deep sided roasting pan over medium-high heat. Brown meat for 3 to 5 minutes on each side or until well browned. Remove roast to a plate. Add onions to pan juices and cook for 2 minutes. Stir in pomegranate juice and half of the cranberries; bring to a boil and boil for 1 minute. Stir in brown sugar, Worcestershire sauce and balsamic vinegar, stirring until sugar is dissolved.
Return roast to pan, turning to coat with sauce. Cover pan and place in oven. Roast for 1 hour, 15 minutes. Stir well and add remaining cranberries. Cover and continue cooking 15 to 45 minutes until roast is tender. Remove from oven and allow roast to rest for 10 minutes. Transfer to serving platter, slice roast and top with sauce.