Prepare 9x13 pan by lining with parchment paper. You will also need a baking tray to create a water bath during baking. Set aside.
Add dates, chopped Jazz apples and water in a saucepan and simmer over medium heat for approx. 15-20 minutes until the fruit is soft and has become a thick sauce. If the mixture is boiling too hard, turn heat down. Stir occasionally to prevent it from sticking to the bottom. Remove from heat and stir in baking soda and almond flavour. Set aside to cool.
In a mixing bowl, cream the butter and sugar together. Add eggs one at a time and then fold in the grated apple. Stir in cooled date/apple mixture. Mix in flour, baking powder and cinnamon until just combined.
Pour into prepared 9x13 pan. Place in a water bath and bake at 350°F for 80-90 minutes. A toothpick will come out clean when the cake is done.