Make the cake. Preheat the oven to 350°F. Spray 2 (8-inch) round springform cake pans with cooking spray.
In a large bowl or stand mixer, mix the almond flour, baking powder, baking soda, and salt. Stir to blend.
In a separate medium bowl, whisk together the eggs, applesauce, coconut nectar or maple syrup, and vanilla.
Pour the wet ingredients into the bowl with the flour mixture and beat until a batter is formed.
Evenly distribute the batter between the prepared cake pans, smoothing on top with a spatula until it reaches the sides. Bake for 25 to 30 minutes until a toothpick inserted into the center comes out clean. Allow the cakes to completely cool in the cake pans before incorporating the custard and frosting.
Make the custard. In a small saucepan over medium heat, slightly warm the coconut cream, about 1 minute. Add the gelatin and whisk vigorously until dissolved. Bring to a simmer. If there are still clumps, that is OK, they should dissolve eventually.
Meanwhile, whisk together the egg yolks and powdered sugar. Once the coconut cream and gelatin mixture is simmering, add half to the yolk and sugar mixture and whisk to combine. Pour it back into the saucepan and whisk until everything is creamy. Continue to cook until slightly reduced, whisking constantly, about 4 minutes. Be sure to watch the saucepan, the mixture can heat quickly and the egg can curdle.
Remove from heat and whisk in the butter and vanilla extract. Add the arrowroot starch and whisk vigorously until dissolved. Alternatively, if there are still clumps, you can transfer the mixture to a blender and process until smooth. Transfer the mixture to a small glass or ceramic bowl. Allow to cool about 1 hour until thickened, stirring occasionally (**see note). Use immediately.
To make the frosting, combine the coconut oil and butter (or vegan butter or palm oil shortening) in a large bowl. Beat with a hand mixer or immersion blender with the whisk tool until fluffy, about 1 minute.
Add the cacao powder or cocoa powder, powdered sweetener, arrowroot starch or tapioca flour and vanilla extract and beat again until everything is combined. Use a spatula to scrape down the sides as you need to.
Using a spatula, mix the frosting. Once ready to compile everything together, spread the vanilla custard evenly between the two cakes. Frost the cooled top cake, spreading the frosting evenly to the sides.