Why did Thomas Cranmer hold his right hand in the fire at his execution?

Thomas Cranmer held his right hand in the fire at his execution as an act of penance because that hand had "offended" by signing false recantations of his Protestant faith.1

While imprisoned under Queen Mary I, Cranmer was pressured to renounce his religious convictions and eventually signed several documents, including an abject recantation of his work in the English Reformation. However, shortly before his death on March 21, 1556, he publicly disavowed these recantations, reaffirmed his Protestant beliefs, and denounced the pope and the doctrine of transubstantiation. By thrusting his right hand into the flames and holding it there until it was consumed, he demonstrated his restored faith and dignity, ensuring that the hand responsible for his betrayal of those beliefs was the first to be destroyed.1