Preheat oven to 180C / 350F.
Place eggs and sugar in the bowl of an electric mixer and beat for 8-10 mins or until very pale and thick.
Sift the flour and baking powder over the mixture and continue to beat at low speed until smooth.
Add the zest and butter. Beat until combined.
Grease two madeleine pans with 12 x 1.5 tablespoon capacity holes. (I used the smaller, bite size ones, which just meant more batches in the oven.)
Spoon mixture into pan and bake for 8-10 minutes or until risen and golden.
Makes 24 (or around 60 with the smaller sized holes).
Recipe adapted from Modern Classics Book 2 by Donna Hay.