Preheat the oven to 180°C (356°F).
Let the melted butter cool.
In a bowl, mix the egg whites and sugar together.
Add the cake flour, almond flour, and baking powder, and mix well.
Add the melted butter to the batter and mix until combined.
Pour the batter into financier molds.
Bake in the oven for 15–20 minutes.
Remove from molds after cooling.