Preheat oven to 190 degrees C (375 degrees F). Grease and flour twenty-four 8cm Madeleine molds.
In a medium bowl beat eggs, vanilla and lemon zest with an electric mixer on high speed for 5 minutes. Gradually beat in the icing sugar. Beat for 5 to 7 minutes or until thick and satiny.
Sift together the flour and baking powder. Sift one-fourth of the flour mixture over the egg mixture, gently fold in. Fold in the remaining flour by fourths. Then fold in the melted and cooled butter. Spoon batter into the prepared molds, filling 3/4 full.
Bake at 190 degrees C (375 degrees F) for 10 to 12 minutes or until the edges are golden and the tops spring back. Cool in molds on a rack for 1 minute. Loosen cookies with a knife. Invert cookies onto a rack and cool. Sift icing sugar over the tops or melt semi-sweet chocolate chips and dip the tips in the chocolate. Store in an airtight container.