Cake: Preheat oven to 180 degrees C. Grease and flour five 20cm round cake tins.
In a large bowl cream the butter with the icing sugar until light and fluffy. Beat in the egg. Stir in the almond essence, salt and ground almonds. Add the flour and mix thoroughly. Divide the dough into 5 equal parts. Pat each piece of dough into a prepared cake tin.
Bake in the preheated oven for 20 minutes, or until delicately browned. Remove from the tins while still hot.
Prune Filling Place the prunes in a saucepan and cover with water. Bring to a boil, remove from heat and let stand for 10 minutes. Drain and reserve the liquid. Grind prunes or puree in a food processor.
In a saucepan, combine ground prunes, white sugar, cinnamon, lemon juice and 4 tablespoons reserved prune liquid. Bring mixture to a boil.
To Assemble: Build the layers with warm prune filling between them. Let stand for 24 hours before slicing.