Preheat the oven to 180°C (356°F).
Mix almond flour, coconut flour, and baking powder in a bowl.
In another bowl, combine eggs, erythritol, vanilla extract, unsweetened yogurt, and melted butter thoroughly.
Combine the dry and wet ingredients to make the batter.
Pour the batter into a pound cake pan.
Bake in the oven at 180°C (356°F) for 25-30 minutes.
Cool, then cut into serving pieces.