Preheat the oven to 375 degrees F. Grease a madeleine pan generously, and lightly dust with flour.
Place the sugar, eggs, and salt in a mixing bowl and whip on medium-high speed until very pale and thick.
Stir in the orange juice. Add the flour and melted butter alternately, folding gently so the batter loses as little volume as possible. Fold in the lavender buds. Refrigerate the batter (covered), for 45 minutes or until thickened.
Scoop the batter into the prepared pan. Bake the madeleines for 12-14 minutes until lightly golden around the edges. Keep the remaining batter refrigerated. Cool in the pan for several minutes, then transfer to a wire rack to cool completely. Dust with powdered sugar and enjoy.