Preheat the oven to 180°C (356°F).
Melt the unsalted butter and let it cool.
In a bowl, mix almond flour, cake flour, sugar, and baking powder together.
Add the egg whites and mix well.
Add the melted butter and combine thoroughly.
Fill the molds about 80% with the batter.
Bake in a 180°C oven for 15–20 minutes.
Let cool before serving.