Wash the kabocha pumpkin thoroughly, remove the skin and seeds, then boil or steam it and mash well.
In a bowl, add eggs and sugar and mix well. Then, add the mashed kabocha pumpkin, milk, and melted butter, and mix evenly.
Sift in the flour and baking powder, and fold gently with a spatula until just combined.
Pour the batter into a cake mold and bake in a preheated oven at 180℃ for 30~35 minutes.
Let the cake cool, remove it from the mold, slice, and serve.