Eggs with sugar (if you like, you can also add 1 sachet of vanilla sugar) and the grated lemon zest on the highest setting until the mixture is creamy-white. Then slowly (as with mayonnaise) let the oil run in and then the liqueur. Then carefully fold in the flour mixed with the baking powder with a spatula - the dough is quite runny. Put in a greased tin (Guglhupf or Kranzform) and bake at 160 ° for about 1 hour (stick test).
For the icing, stir the lemon juice with the icing sugar until creamy and brush onto the cooled cake.
This cake stays juicy for a week, if it survives that long.