In a small bowl, combine the coconut flour, cocoa powder, and baking powder.
In another bowl, add the chocolate and butter and melt in a microwave for 5-10 sec intervals, stirring well in between. Stop when a few pieces of chocolate are still left; they will melt from the heat of the mixture.
When the chocolate has melted, add the sweetener, vanilla, and salt. Mix well. Then, add the whisked egg while mixing continuously. Keep mixing until a homogenous consistency is reached.
Add the dry ingredients and mix until no dry ingredients are left.
Split the batter between two standard 6oz (170ml) ramekins and microwave for 60-70 sec at full power (1000 watt) until risen and just firm on the top. A few wet spots on the top of the mug cakes are okay. If you microwave for too long, the cake will come out dry.
Serve with fresh berries, powdered sugar, and/or freshly whipped cream.