Preheat the oven at 350˚F, and lightly grease 6 wells of a large muffin tin.
In a saucepan over low heat, melt the butter slowly.
Using an electric mixer, beat the egg whites and cream of tartar until soft peaks form.
In a separate bowl, combine the egg yolks, butter, baking powder, and almond flour. Mix well.
Gently fold the flour mixture into the egg whites until thoroughly combined.
Pour the batter into 6 muffin wells, and bake for about 20 to 30 minutes or until golden brown.
Cool completely on cooling rack before serving. Store in the fridge for up to 5 days