Cut the butter into small pieces and put in a heavy saucepan over medium heat.
Once melted reduce to low and cook the butter for a further 10 minutes until browned.
Pour into a bowl and add vanilla extract and lemon zest. Set aside.
In a medium bowl whisk together the flour, baking powder and salt. Set aside.
In a separate bowl beat the eggs and sugar until it reaches the ribbon (about 4 minutes - should be thick and pale in color).
Now fold the dry ingredients into the egg mixture in 3 batches taking care not to over mix.
Lastly fold in the melted butter and refrigerate for 4 hours or up to 2 days. 30 minutes before baking take your mixture out the refrigerator.
Butter your Madeline own and sprinkle with flour. Bake are 375 degrees for 14 minutes. Leave them to cool for 10 minutes before removing from the pan.
Dust with confectioners sugar or dip in chocolate.