Mash the banana.
Mix the eggs and mashed banana well.
Add melted butter and milk, then combine.
Sift in sugar, cake flour, matcha powder, baking powder, and salt.
Mix the ingredients thoroughly.
Pour the batter into a brownie pan.
Bake in a preheated oven at 180°C for 25–30 minutes.
Once cooled, cut into desired serving sizes.