Preheat the oven to 350 degrees fahrenheit and grease an 8x8 baking dish.
In a large bowl, combine the sliced apples, maple syrup, arrowroot, lemon juice, vanilla, cinnamon, and nutmeg. Stir to combine completely and make sure all the apples are coated evenly.
In a separate bowl, whisk together the flour, oats, coconut sugar, and baking powder.
Once combined, add the cubed butter and use a fork to break it up completely until you reach a crumbly consistency.
Pour the apple mixture into the greased pan, followed by sprinkling the crumble topping over the apples evenly.
Bake for 35-45 minutes until bubbling on the sides and slightly golden on top.
Remove from the oven and let cool for 10-15 minutes before serving.