Prick the duck all over with a fork. Rub a little salt into the duck skin and place on a trivet in a roasting pan. Roast for 1½ - 1¾ hours at 375 deg F (180 deg C) without basting. Meanwhile cut the skin including the pith off the UGLI® tangelo. Carefully slice the fruit into slices and cut in half. Gently poach the fruit in Cointreau for 4-5 minutes then pour the remaining delicious juice over the duck when cooked on the serving plate. Garnish with the fruit slices, watercress and duchesse or mashed potatoes.