Combine first 6 ingredients in a large bowl. Beat with a mixer at medium speed for 5 minutes or until mixture is thick and pale. Sift cake flour over egg mixture, 1/2 cup at a time; gently fold in flour. Fold in melted butter. Cover and refrigerate at least 1 hour.
Preheat oven to 350°.
Spoon about 2 teaspoons batter into each of 12 madeleine molds or other cookie molds coated with baking spray. Bake at 350° for 8 minutes or until golden around edges. Cool in pan on a wire rack 2 minutes. Remove from pan, and cool completely on wire rack. Repeat procedure twice with the remaining batter to yield 36 madeleines. Dust madeleines with powdered sugar.