Slice the butter into tablespoon-sized pieces. Melt the butter in a saucepan over medium heat or in a large bowl in the microwave in 20-second increments. Set aside to cool slightly while you prepare the batter.
In the bowl of a stand mixer fitted with a whisk attachment or in a large mixing bowl using a handheld mixer, beat the eggs, egg yolk, granulated sugar, and brown sugar on medium-high speed for 5 to 7 minutes or until thickened and light in color. When you lift your beaters up, you should see ribbons of the mixture as it’s falling back into the bowl.
Mix in the vanilla extract and lemon zest until just combined.
Sift half of the flour, baking powder, and salt over the wet ingredients and fold it in until just combined. Then, sift in the remaining half of the dry ingredients and gently fold it in.
Carefully pour half of the cooled melted butter over the batter. Fold the butter into the batter until just combined. Add the remaining melted butter and fold it in until just combined and no streaks remain.
Cover the batter and transfer to the refrigerator to chill for 30 minutes. This will result in a fluffier madeleine, so don’t skip this step!
Preheat the oven to 375°F (190°C). Brush each cavity of a madeleine pan with melted butter. If you have two pans, you will want to grease 20 cavities with melted butter.
Scoop a heaping tablespoon of the batter into each greased cavity. No need to smooth the batter out, it will spread in the oven as it bakes.
Bake for 8 to 10 minutes or until a toothpick inserted into the center of the madeleines comes out clean.
Remove from the oven and carefully invert onto a wire cooling rack to cool slightly.
Dust with powdered sugar right before serving.
Video
Notes
Storage Instructions: Madeleines are best enjoyed fresh, but you may store them in an airtight container at room temperature for up to 1 day.