Preheat oven to 375'F. Lightly grease a 9x13 baking dish and set aside
For the filling, combine apples, golden monk fruit, lemon juice, vanilla, nutmeg, cinnamon, almond flour, coconut flour, xanthan gum, and salt in a large bowl. Toss with a rubber spatula until apple cubes are lightly coated.
Transfer apples to baking dish, arranging them evenly across the bottom.
For the crumble, combine almond flour, coconut flour, golden monk fruit, and oats in a bowl. Whisk together.
Cut butter into flour mixture to form a crumble.
Add egg white to crumble mixture, mixing until fully incorporated.
Drop the crumble evenly over the top of the apples in the baking dish. Sprinkle with cinnamon.
Bake in preheated oven for 35 minutes or until the crumble is just golden. Do not over-bake. Crumble may appear soft when first removed from oven but will crisp up as it cools.