Preheat the oven to 325F.
In a bowl, mix together the almond meal, coconut sugar, coconut oil, egg yolk, vanilla and salt. Use your hands to knead the dough to make sure everything is evenly mixed. Form it into a ball.
Place the dough on the parchment-lined baking sheet and press into a square shape. Use a rolling pin (or wine bottle!) to roll the dough out until it’s about ¼-inch thick.
Layer the apples on top of the dough and gently press them down. Use a brush (or a paper towel or napkin) to spread a thin layer of the egg wash on top of the apples (helps them get nice and brown). Sprinkle with cinnamon and top with chopped hazelnuts, if using.
Bake for 25-30 minutes, or until the edges of the dough are deeply golden.
Serve warmed topped with vanilla ice cream! I also enjoy it for breakfast cold or warm with plain whole milk yogurt on top!