Preheat the oven to 180°C (356°F).
Melt the butter and let it cool.
Add egg whites to a bowl and whisk lightly.
Sift almond flour, cake flour, sugar, and salt into the egg whites and mix together.
Add the melted butter and mix well until smooth.
Pour the batter into financier molds.
Bake in the preheated oven at 180°C (356°F) for 12-15 minutes.
Transfer to a wire rack to cool.