Step 1
Preheat oven to 375 degrees F (190 degrees C).    Butter and flour 12 (3 inch) madeleine molds; set aside.
Step 2
Melt butter and let cool to room temperature.
Step 3
In a small mixing bowl beat eggs vanilla and salt at high speed until light.
Step 4
Beating constantly gradually add sugar; and continue beating at high speed until mixture is thick and pale and ribbons form in bowl when beaters are lifted 5 to 10 minutes.
Step 5
Sift flour into egg mixture 1/3 at a time gently folding after each addition.
Step 6
Add lemon zest and pour melted butter around edge of batter.  Quickly but gently fold butter into batter.  Spoon batter into molds; it will mound slightly above tops.
Step 7
Bake 14 to 17 minutes or until cakes are golden and the tops spring back when gently pressed with your fingertip.
Step 8
Use the tip of the knife to loosen madeleines from pan; invert onto rack.  Immediately sprinkle warm cookies with granulated sugar.  Madeleines are best eaten the day they're baked.  Leftover madeleines are wonderful when dunked into coffee or tea.
Step 9
Variation: Chocolate Madeleines: Omit lemon zest.  Increase sugar to 1/2 cup.  Substitute 1/4 cup unsweetened cocoa powder for 2 tablespoons of the flour; sift into batter with flour.