Eggs must be at room temperature, and the butter is softened. In a deep pot mix to the butter with the sugar until the acquisition of light and fluffy cream. In separate bowl beat eggs slightly and then add them to the cream, while stirring, until thick and shiny mixture. Mix flour with baking powder and add them to the mixture along with vanilla, lavender flowers and milk, stirring with a wire whisk until ingredients are homogeneous. Pour the dough in a buttered and floured cake pan measuring about 20 cm. and bake in a preheated oven 180C degrees to a golden-brown color. Test the readiness of the cake with a toothpick. Then let it cool and remove it from the form. Mix in a separate cup powdered sugar with water and stirring until a nice smooth consistency, which decorate the cake. Optional decorate with fresh lavender flowers.