Preheat the oven to 180°C.
Mix almond flour, cocoa powder, baking powder, and salt in a bowl.
In another bowl, whisk together eggs and erythritol.
Combine the mixtures from both bowls and mix well.
Add melted unsalted butter and dark chocolate, then mix evenly.
Pour the batter into a baking pan.
Bake in the oven at 180°C for 20–25 minutes.
Let it cool before serving.