Finely chop the dark chocolate.
Melt the butter using a double boiler.
Sift the unsweetened cocoa powder and almond flour together.
Crack the eggs into a bowl and beat well.
Mix the chopped chocolate, melted butter, and beaten eggs.
Add the cocoa powder and almond flour and mix until well combined.
Pour the batter into the cake pan.
Bake in a preheated oven at 180°C (356°F) for 25 minutes.