To make Madeleines: Preheat oven to 325 degrees F. and spray Madeleine pan generously butter and flour a Madeleine pan (preferably non-stick), knocking out excess flour.
In a bowl sift the flour, baking powder, salt, and zest together.
In another bowl with an electric mixer beat together butter, lemon juice, and sugar until mixture is light and fluffy. Add the lemon zest. Beat in eggs, 1 at a time, beating well after each addition, and add flour mixture, beating until just combined.
Spoon some of the batter into prepared Madeleine molds, filling the mold 3/4 full. Using both hands, pick up the Madeleine tray and lightly tap against the table to spread the batter evenly. This will eliminate any air pockets and ensure that molds are not overfilled.
Bake Madeleines in middle of oven 20 to 25 minutes, or until edges are browned and tops are golden. Loosen edges and transfer Madeleines to a rack set over a baking dish. Make more Madeleines in pan, cleaned and freshly sprayed.
To make lemon syrup: While first batch of madeleines is baking, in a small saucepan bring syrup ingredients to a boil, stirring, and remove from heat.
Brush warm madeleines with some of hot syrup and repeat with remaining madeleines as they are baked, keeping syrup warm.