Whisk flour, baking powder, and salt together and set aside.
With an electric mixer with a whisk attachment, beat eggs and sugar together until pale and doubled in volume.
Add vanilla and mix just until blended.
With a spatula, gently fold in the flour mixture until well blended.
Pour a small amount of the egg mixture into a bowl and add the butter. Slowly and gently fold it in.
Blend into the larger egg mixture.
Cover and chill for at least an hour. Overnight is fine.
Brush a generous amount of butter into each cavity of the madeleine pan.
Spray with a small amount of Baker's Joy or other spray containing flour.
Using a small scoop, fill each cavity with batter. Smooth out with an offset spatula.
Chill for one hour.
Preheat oven to 350°.
Bake for 9-10 minutes, or until edges are browned and tops spring to the touch.
Flip madeleines out onto parchment and allow to cool.
Sprinkle with confectioners sugar.
Keep in an airtight container until ready to serve.
They are great the next day if microwaved for about 15 seconds.