Preheat the oven to 400 degrees F. Butter and flour 2 madeleine pans.

In a medium sized mixing bowl, beat the eggs. Add the sugar, sour cream, and lemon zest. Sift in the flour and baking powder; whisk to combine, and then whisk in the melted butter until smooth.

Pour the batter into a large piping or ziploc bag, snip off the tip or corner, and divide the batter between 18 madeleine molds.

Bake for 10-15 minutes, or until golden brown around the edges and risen in the centres. Sift the warm madeleines with icing sugar, and gently turn or lift out of the pans onto a wire rack to cool.