Melt the butter and set aside to let cool.

Place the madeleine mold into the freezer.

Beat eggs and sugar together until they reach the ribbon stage. Using a mixer on high should get you to this point between 5 - 10 minutes. A good test is to lift the mixer blades out of the mixture and let it drip back to the batter. It should take a count to three to fully integrate back with the mixture.

At this point, add vanilla and mix again.

Sift the flour over the batter and fold or stir into the mixture.

Add the lemon zest to the butter and stir. Now pour 1/2 of the lemon butter into the mixture. The best technique is to pour the butter in along the edge of the batter.

Use a rubber spatula to carefully fold the butter and mixture together. Once integrated, add the remainder of the butter.

Let this batter sit in the fridge at least 20 minutes. You can also let it sit overnight.

Heat the oven. If using a dark madeleine mold, heat oven to 350. If using a light silver, or rubber mold, heat oven to 375. (The dark molds heat faster.)

Butter and flour the molds and fill the molds to 3/4 with batter.

Place in oven and bake for 8 - 10 minutes. At 7 minutes, I would start keeping a good watch on them. You want the little cakes to have a spring-back feel to their bellies. When done, immediately remove from oven and pop out of molds. Cool on a wire rack, belly-up. Don't worry if their shell side seems a litle dark. This is relatively normal for a madeleine.

After they have cooled for about 10 minutes, turn over, and if you like, sprinkle with powdered sugar.

Enjoy !!