Put the sugar and the eggs in a large bowl and whisk with the electric whisk. Add the melted butter and the limoncello and continue turning. Add the grated lemon rind, flour and baking powder. Mix everything well until it is homogeneous. Line a baking sheet with baking paper and pour the mixture. Bake for about 40-45 minutes and when it is cooked, leave to cool.

For the limoncello cream, whip the sugar and egg yolks with an electric mixer until the mixture is frothy and white. Add the milk and the flour and continue stirring. At the end add the limoncello and the lemon zest.

Pour the mixture into a saucepan and cook over low heat, stirring constantly, until it thickens. At this point the cream is ready, let it cool.

Cut the cake into two or three disks, depending on the height of the cake and fill with the limoncello cream. Decorate the cake with cream and lemon slices on top.