Preheat the oven to 180 (356 Fahrenheit). Pour hot water over orange peel, drain the excess water, and chop into small pieces. Cut the banana into 5 pieces.
Add the bread flour, cocoa powder, sugar, salt, and baking soda, then mix using hands. When there are cocoa and sugar lumps, crush them with your fingers and mix well.
Add the vegetable oil, water, vinegar, and vanilla oil, then briefly mix with a fork until they are well blended. Please be careful not to mix too much.
Divide the batter in half. Mix the chopped orange peel into one portion.
Place paper cups in the pan, and pour in the Step 4 batter. Place the banana slices on top of the plain ones (without the orange peel).
Bake in the oven for 25 minutes at 180 (356 Fahrenheit).