Wash the kabocha squash thoroughly, remove the seeds, and steam it with the skin on.
Let the cooked kabocha cool and mash it.
Put butter and sugar in a bowl and cream them together.
Add eggs and mix well, then add the mashed kabocha.
Sift flour and baking powder into the batter and mix.
Pour the batter into a pound cake mold and bake in a preheated oven at 180°C for 40 minutes.