Melt the dark chocolate and butter using a double boiler.
Whisk together the eggs and erythritol until frothy.
Add yuzu marmalade to the melted chocolate butter mixture and mix well.
Sift in the dry ingredients (almond flour, cocoa powder, baking powder).
Mix the batter and pour it into a baking pan.
Bake in a preheated oven at 180°C for 20 minutes.