Pre-heat the oven to 350 degrees and lightly grease and flour an 8x8 baking dish.
In a small bowl, whisk together the chickpea flour, gluten-free flour, baking powder, baking soda, cinnamon and salt.
In a mixing bowl, combine the butter, sugar and maple syrup. Mix on medium speed for 2 minutes.
Add the vanilla extract and the eggs, one at a time, to the mixing bowl. Scrap down the sides and mix to incorporate between each addition.
Mix in half of the flour mixture, then the buttermilk, then the remaining flour. Continue to mix until the batter is just combined.
Pour the mixture into the prepared baking dish.
To make the crumble, combine all ingredients in a bowl. Use your fingers or a fork to mix it together into a crumbly mixture. Sprinkle evenly on top of the cake batter then bake for 40-45 minutes until a toothpick inserted in the center comes out clean.
Allow cake to cool slightly before serving.