Preheat the oven to 350 degrees. Lightly grease a 9x11 or 8x11 baking dish and set aside.
In a large bowl, mix together the blueberries, coconut sugar, lemon zest, and arrowroot starch. Add the lemon juice, gently stirring to combine. Let sit for about 5 minutes.
In a medium bowl, mix together the almond flour, pecans, coconut sguar, cinnamon, and salt. Fold in the butter or ghee, and stir to combine, using a fork or pastry knife if necessary.
Pour the blueberry mixture into the prepared dish. Spoon the crumble topping evenly across the top of the dish. Transfer to the oven and bake for 25-28 minutes, or until bubbly. The 25 minute mark will produce a softer and chewy topping, letting it bake a few extra minutes will create a crunchier topping.
Serve warm plain or with vanilla ice cream. Store at room temperature, do not refrigerate.
*use coconut oil for a vegan option