Preheat oven to 350 degrees F. Cut piece of aluminum foil large enough to wrap brisket. Sprinkle half of diced onions over foil in layer about same size as brisket. Set brisket over onions. Sprinkle remaining onions over top. Seal tightly. Set in large shallow pan. Roast 3 hours. Combine beer with remaining ingredients in large saucepan and bring to boil over medium-high heat. Remove from heat. Discard foil and spread fruit mixture over brisket. Reduce oven to 300 degrees F. Cover pan and continue roasting 1 hour, adding more beer to pan if sauce appears too dry. Transfer brisket to heated platter. Surround with fruit and sauce.