Preheat the oven to 350 degrees Fahrenheit. Grease an 8x8 baking dish with cooking spray.
Combine blackberries, maple syrup, and a ½ teaspoon vanilla extract in a medium bowl and set aside.
Add cane sugar, oats, cinnamon, pinch of salt, and cassava flour to a second medium bowl and whisk to combine. Use a fork, pastry cutter, or your fingers to cut in pieces of vegan butter into the crumble. You will have pea-sized pieces when finished. Add remaining vanilla extract and toss mixture to coat.
Transfer the fruit mixture to the prepared baking dish. Sprinkle gluten-free crumble topping over the fruit in an even layer.
Bake for 30-35 minutes or until top is a golden brown and blackberry mixture is bubbling. Allow blackberry crumble to cool for a few minutes before serving.
Serve with vanilla ice cream or coconut whipped cream.