Preheat the oven to 180°C (356°F).
Melt unsweetened dark chocolate and butter together using a double boiler.
Add erythritol to the melted chocolate and butter, and mix well.
Add eggs one at a time, stirring well after each addition.
Add almond flour, baking powder, and salt, and mix evenly.
Pour the batter into a brownie pan.
Bake in the preheated oven for 20-25 minutes.
Let it cool completely before removing from the pan and serving.