Preheat your oven to 325°F. Grease a round 9-inch cake pan generously with cooking oil spray and set it aside.

In a food processor or blender, place the coconut palm sugar and tapioca starch, and pulse or blend until the sugar is finely ground. Set aside.

In the bowl of a stand mixer fitted with the whisk attachment, or a large clean bowl with a hand mixer, place the egg whites. Whip until frothy, add the cream of tartar and continue to whip until stiff, but not dry, peaks form. Transfer the whipped egg whites to a separate small bowl and set them aside.

In the same large bowl or bowl of your stand mixer fitted with the paddle attachment, place the almond flour, ground coconut sugar, salt, and baking soda, and whisk to combine.

Create a well in the center of the dry ingredients, and add the egg and egg yolk mixture, and the vanilla. Beat until smooth and fully combined. The mixture will be thick.

Add about 1/2 of the whipped egg whites to the thick batter, and mix until fully combined. The batter will still be thick, but the whipped egg whites should have lightened it a bit.

Add the remaining whipped egg whites, and using a spatula, carefully fold them into the batter, taking care not to deflate them too much. The batter should be smooth and relatively light.

Pour the batter into the prepared cake pan and smooth the top with an offset spatula or another flat spreader. Smack the pan on the counter once or twice to break any very large air bubbles.

Place the pan in the center of the preheated oven and bake for about 22 minutes, or until the cake is set in the center and a toothpick inserted comes out with no more than a few moist crumbs attached.

Allow the cake to cool in the pan for about 10 minutes before turning out onto a wire rack to cool completely.

The cooled cake can be wrapped tightly and stored in the freezer, or topped with some coconut whipped cream and berries, and served immediately.