Whisk flour, baking powder and salt together in a large mixing bowl. Set aside;
In a separate bowl, whisk oil, buttermilk and egg; pour this over reserved flour mixture. Stir lightly with your fingers until the ingredients come together to form a fairly smooth dough. If your dough is too soft, add extra flour until you reach the desired consistency. Your dough should be soft, slightly tacky, but not sticky.
Transfer dough onto a piece of plastic wrap. Press down to form into a thick disc, wrap and refrigerate for at least 30 minutes.
For the filling
Preheat oven to 375F.
On floured surface, roll out dough to form a 12-13 inch disc. Fit into 9 inch spring form pan, letting excess hang over edge; Set aside.
Cut the apples in half and remove their core with a melon baller. Slice the apples as thinly and uniformly as you can; the use of a mandolin is strongly recommended. Reserve the prettiest slices for the top layer (the equivalent of about 2 apples).
Arrange your apple slices in layers, working your way up in a somewhat circular pattern. No need to be super fancy until you get to the very last layer, but still, you want to keep your layers as level as possible.
When you get about halfway up, sprinkle half the raisins and half the pecans, and then resume piling slices of apples. Make sure to make the final layer super pretty and sprinkle the rest of the raisins and pecans; Fold excess dough back over the apples and set aside.
In a large mixing bowl, delicately mix the date paste, arrowroot and eggs with a whisk until smooth and well combined. Whisk in egg whites, followed by buttermilk, coconut water, cinnamon, nutmeg and vanilla. Whisk until all the ingredients are fully incorporated then slowly pour that mixture right in the center of your cake. Don't pour too quickly: you want the mixture to get between all the apple slices while avoiding getting too much of it on top of your cake.
Place in the oven immediately and bake for 40-45 minutes, until the crust turns nice and golden brown and the cake is set.
Turn the oven off and crack the door open. Let the cake cool in the oven for a couple of hours, then chill completely in the refrigerator for at least 6 hours, preferably overnight before very delicately removing from pan.