In a small bowl mix together the dry ingredients: flour, baking powder, salt. Set aside.
In a larger bowl whisk the sugar with the eggs to obtain a pale yellow mix. Add the melted butter and the dry ingredients to obtain a smooth cream. Add also the orange zest.
Refrigerate the batter in the fridge for at least 1 hour.
Grease a Madeleine tin brushing some butter inside the shells.
Pour 1 Tbsp of mix inside of each shell. Do not spread.
Bake in preheated oven to 350F/180C for 8 minutes. Remove from the oven, let cool down 5 minutes and remove from the pan. Dust with powdered sugar before serving.