NINOSHIMA, Japan (AP) — Baumkuchen originated in Germany but has become a wildly popular sweet in Japan, where a prisoner of war on a small western island started making the treat that has thrived in its new homeland. Today, the confectionery known as “tree cake” because of the resemblance to a trunk with rings is considered a symbol of longevity and prosperity in Japan, where Baumkuchen festivals are regularly held. Japanese adaptations, including those using maccha and sweet potatoes, are