Preheat the oven to 180°C (356°F).
In a bowl, combine Extra Brut cocoa powder, cake flour, baking powder, and salt. Mix well.
In another bowl, cream the butter and sugar together.
Add the eggs and mix well.
Add the dry ingredients to the butter mixture.
Add the milk and vanilla extract, and mix until evenly combined.
Pour the batter into a baking pan.
Bake in the preheated oven for 20-25 minutes.