Ingredients:
3 tsp orange zest
6 egg whites
6 egg yolks
2 tsp baking powder
1 1/2 cups cake flour
1 cup confectioners’ sugar
1/2 tsp cream of tartar
1/2 tsp salt
1 tsp vanilla extract
1 cup white sugar
1/2 cup fresh orange juice
5 tbsp butter, softened