Set your oven to 375°F and grease an 8x8-inch baking pan.

In a small bowl, gently toss the blueberries with coconut sugar, lime juice, and arrowroot. Set aside.

Make the crust and crumble.

Using an electric mixer, combine flour, coconut sugar, baking powder, butter, and egg. Mix until the dough is moist but crumbly.

Divide the dough in half. Press one half evenly into the bottom of the greased pan to form the crust. Spread the berry mixture over the crust, then sprinkle the remaining dough over the berries to create the crumble topping.

Bake for about 45 minutes, or until the berry juices are bubbling and the crumble topping is lightly browned.

Let the bars cool completely before cutting, or serve them warm with a scoop of vanilla ice cream for an extra treat!