Preheat oven to 350 degrees and spray two madeleine pans with non-stick spray.
Place butter in a microwave safe dish and microwave in 30 second intervals until completely melted. Set aside to cool.
Combine sugar and eggs in a bowl and mix on medium-low speed using an electric hand-held mixer. Mix well until slightly foamy. Next, add flour and baking soda, and mix until combined. Then add melted butter and lavender extract.
Add about one tablespoon of batter to each of the shell-shaped cavities on the madeleine pans. Bake for 8-10 minutes, or until edges are golden brown and the tops of the madeleines no longer jiggle.
Let the madeleines cool in the pans for a few minutes, then gently remove them from the pans with a knife and let them finish cooling on a wire rack.