Sift the matcha powder, cake flour, and baking powder together.
Soften the butter at room temperature and cream with sugar.
Add eggs one at a time, mixing well after each addition.
Add the sifted dry ingredients and mix until combined.
Add chopped dark chocolate and mix in.
Pour the batter into a loaf pan lined with parchment paper.
Bake in a preheated oven at 180°C (356°F) for 35–40 minutes until done.