By John O’Brien SINGAPORE (Reuters) – An old proverb states that ‘revenge is a dish best served cold’ but Dominika Cibulkova’s service was smoking hot when she exacted vengeance on Angelique Kerber to claim the WTA Finals title on Sunday. The German world number one had beaten the Slovakian in a tight three-setter a week ago when they faced off in round-robin play but Cibulkova saw enough in that losing effort to give her the confidence to turn the tables on her opponent in the final. The 27-year-old hassled and harried Kerber from the very first game and after a 76-minute serving masterclass, Cibulkova was rolling around the court in stunned disbelief after claiming the biggest victory of her career, following a 6-3 6-4 triumph.