Preheat the oven to 350°F.
Prepare the Madeleine pan: melt 3/4 tablespoon butter, then mix in the 1/2 tablespoon flour.
Using a pastry brush, “paint” the insides of the molds with the butter and flour mixture.
Using a hand-held mixer, beat the egg and sugar together until they become thick and pale.
Whisk together the flour and baking powder, then sprinkle onto the egg mix and gently fold in.
Add the melted butter, clementine zest and clementine juice; gently fold into the egg mixture.
Fill Madeleine molds two-thirds full (a heaping teaspoon), and bake for 11 minutes.
When they are golden around the edges, remove them from the oven and let cool 2-3 minutes.
Using a thin spatula, loosen the edges and push the Madeleines out to cool on a rack.
Dust with confectioner’s sugar.
Makes 12 Madeleines