Add the sugar, mustard, celery seed, salt and pepper to the pot and cook for another minute. Add the minced garlic and cook another minute. Deglaze the pan with the malt vinegar and lambic, leave behind any yeast from the bottle conditioning, stirring to remove any fond (brown bits on the bottom of the pan). Add the tomato purée and stir until combined. Bring the tomato mixture to a slow simmer, stirring occasionally over low heat. Since the tomato puree has been reduced, a higher cooking temperature can burn the bottom of the pot if not stirred often.