In a small mixing bowl, beat eggs, vanilla and salt at high speed until
light.
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.
Sift flour into egg mixture 1/3 at a time, gently folding after each
addition.
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.
Bake 14 to 17 minutes, or until cakes are golden and the tops spring back
when gently pressed with your fingertip.
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.