In small saucepan over medium heat, cook butter until foam subsides, whisking constantly. Continue cooking until butter has a deep brown color, about 3-5 minutes. Remove from heat immediately and transfer to a small bowl to stop cooking; set aside to cool to room temperature.

In small bowl, combine flour, baking powder and salt; set aside. In large bowl, beat eggs and sugar with electric mixer on medium-high speed until thickened and pale yellow in color, about 5 minutes. Add lemon zest and juice. Using a spatula, fold flour mixture into egg mixture in three additions. Fold in cooled butter. Cover with plastic wrap and refrigerate at least 30 minutes and up to 1-1/2 hours.

Preheat oven to 375°. Generously butter cavities of Madeleine Pan. Scoop 1 tablespoon batter into each cavity. Bake 8-9 minutes or until edges are golden brown. Immediately transfer madeleines to cooling grid, shell side up. Cool completely. Dust with confectioners’ sugar, if using.