Preheat oven to 350F/176C Mix sugar and eggs until they are pale yellow.
Add zest. Now Mix dry ingredients and add to the egg mixture until well combined.
Add the melted butter to the bowl. Now The batter should be refrigerated for at least one hour. You can even leave it in the fridge overnight. This is crucial to get the “hump”, the French trademark of the Madeleine, which you need to bake.
This technique will lightly coat a nonstick Madeleine pan using the baking spray. Lightly grease each well with the baking spray. Place 1 tbsp (15ml) of batter in the middle of each well. Don’t touch it. The batter will expand by itself and take a uniform shape.
Bake for 7-8 minutes until edges are slightly golden and the center has a slight hump. Let cool, then take out of the tin. Cool completely. After cooling completely, dust the top with powdered sugar. These can be eaten right away, as they taste best the day they were made. Now You can make the batter up to two days in advance.