1. Beat the egg whites until stiff. 2. Add the zest of lemon, the caster sugar and the flour. 3. Melt 50g of butter and add the previous mixture. 4. Butter the mold with the remaining butter. Stir the mixture gently into the baking pan 6. Put in the oven T 5-6 baking 30min. 7. Allow the cake to cool before unmolding 8. Finally sprinkle the icing sugar cake with a colander.