Gently boil the oranges in water for 2 hours. Cool and puree, skins included (remove as many seeds as possible before pureeing).
Beat eggs and caster sugar until sugar has dissolved. Add pureed orange. Preheat oven to 180 degrees C.
Mix together almond meal and baking powder. Folk through the orange-egg mixture. Pour into a greased ring tin. Bake 1 hour and allow to cool.
Combine sugar, orange juice, peel, cinnamon stick and star anise in a non-reactive pan. Simmer gently until a smooth syrup is achieved (about 15 mins). Remove cinnamon, peel and star anise and stir through the butter. Serve cake dusted with icing sugar on a pool of citrus sauce.