1stick (4 ounces) unsalted butter, melted until browned
1and 1/2 teaspoons lemon zest, finely grated
1and 1/4 teaspoons baking powder
3large eggs, at room temperature
1/2cupconfectioners sugar, sifted, optional
Cut the butter in tablespoons and place them in a heavy saucepan over medium heat. Once the butter has melted, reduce the heat to low and continue cooking, until the solids sink to the bottom of the pan and turn golden brown, about 10 minutes. Remove from heat and pour the browned butter into a small bowl. Stir the vanilla and lemon zest into the butter, then set aside to cool.
In a medium mixing bowl, whisk together the flour, baking powder, and salt. Set aside until needed.
In the bowl of a stand mixer fitted with the whisk attachment, beat the eggs at medium speed while gradually adding the sugar. Once all of the sugar has been added, increase the speed to medium-high and continue whipping the mixture until it's very thick and pale in color, about 3 to 4 minutes. Turn the mixer off and, using a silicon spatula, fold in the flour mixture in three additions, stirring just until combined. Fold in the butter mixture.
Cover the bowl and refrigerate for at least 4 hours, and up to 2 days.
30 minutes before you're ready to bake, preheat the oven to 375 degrees (F). Generously brush the molds of your madeleine pan with butter, then lightly dust with flour.
Using a medium cookie scoop, spoon level scoops of the batter into the center of each mold. You don't need to spread the batter.
Bake for 12 minutes, or until the "bellies" have risen and they're golden brown.
Cool madeleines in the pan placed on a cooling rack for a minute or two, then gently loosen them from the molds. If they stick, carefully run a small knife around the edge of the cakes until they release.
Dust with confectioners' sugar and serve warm, with coffee or tea.