Preheat the oven to 180°C (356°F).
Mash the banana, then add the eggs, almond flour, cocoa powder, and baking powder. Mix well.
Add stevia and mix evenly.
Pour the batter into an oven-safe container or pan and spread it evenly.
Bake in the oven at 180°C (356°F) for 20 minutes.
Let it cool before serving.