1. Whisk egg whites, cream of tartar and caster sugar together until fluffy. Set aside.
2. Preheat oven to 180°C.
3. Cream butter and condensed milk together. Add in the remaining ingredients.
4. Fold in the egg white mixture from step 1.
5. Bake in a preheated oven. Use a small greased tin (7”x7”) for best results. Spread the cake mix thinly to coat and cover the cake tin. You only need a small amount of about 40g to get thin layers.
6. Bake the first layer at 180°C, using top and bottom heat. Bake the second layer using top heat only at 200°C. For the third layer, lay some of the prunes in a row on top of it and bake. Bake the third layer at 180°C using top and bottom heat. Repeat till all the batter is used. Thereafter, bake the whole cake for 5mins at 180°C, top and bottom heat.