Melt the butter over medium heat until it turns brown.
In a bowl, combine egg whites, sugar, and salt and mix with a whisk.
Sift in almond flour, rice flour, and baking powder, then mix together.
Add the melted butter and stir until the batter is evenly combined.
Let the batter rest in the refrigerator for 30 minutes.
Pour the batter into financier molds.