In a small saucepan, melt the butter and then keep it warm.

In a small bowl whisk together the flour, baking powder, and salt.

In the bowl of your electric mixer, or with a hand mixer, beat the eggs and sugars at high speed until the mixture is thick and pale in color (about 5-8 minutes). Beat in the vanilla extract and orange or lemon zest.

Then sift about one-third of the flour mixture over the whipped eggs and gently fold in, using a rubber spatula or whisk. Sift and fold in half of the remaining flour, and then sift and fold in the rest. (Do not over mix or the batter will deflate).

Then take about 1/2 cup (125 ml) of the batter and fold it into the warm melted butter. (This lightens the butter making it easier to fold into the batter.) Then, with a spatula, gently fold the butter mixture completely into the egg batter.

Cover and refrigerate the batter for at least an hour or two, preferably overnight (can be stored in the refrigerator for up to three days).

Preheat your oven to 375 degrees F (190 degrees C). Using a pastry brush, generously grease the molds Madeleine pans (preferably non-stick) with very soft or melted butter.

Then dust the molds with flour, tapping out the excess flour. Refrigerate the pans until the butter hardens (about 10 minutes). (Make sure the pans are well greased or the Madeleines will stick and be hard to remove.)

Drop a generous tblsp full (can use an ice cream scoop) of the batter into the center of each prepared mold, leaving the batter mounded in the center. (This will result in the classic "humped or domed" appearance of the Madeleines.)

Bake the Madeleines for about 8 to 10 minutes, until the edges are golden brown and the centers spring back when lightly touched. (Do not overbake these cookies or they will be dry.)

Remove the pans from the oven and immediately tap each pan against the counter to release the Madeleines. Place Madeleines on a wire rack to cool.

Best served immediately but can be stored in an airtight container at room temperature for a couple of days or frozen for up to 1 month. Dust with powdered sugar before serving enjoy with tea or coffee.