Prep the oven and pan: Preheat the oven to 350°F (175°C). Grease a 9-inch pie dish with butter or spray.

Make the crust/crumble dough: In a large bowl, whisk almond flour, coconut flour, sweetener, baking powder, and salt. Add melted butter, egg, vanilla, and almond extract. Stir until a soft, slightly crumbly dough forms.

Form the base: Press about 2/3 of the dough evenly into the pie dish, going up the sides. Use the back of a spoon or your fingers to smooth it. Prick the base with a fork a few times to prevent bubbling.

Par-bake the crust: Bake for 10–12 minutes until just set and lightly golden at the edges. Remove and let it cool for 5 minutes.

Prepare the filling: In a bowl, toss blueberries with sweetener, lemon juice, zest, vanilla, cinnamon, and a pinch of salt. Sprinkle xanthan gum evenly over the berries and toss again so it doesn’t clump. If using almond flour instead, mix it in thoroughly.

Fill the crust: Spoon the blueberry mixture into the par-baked crust. Spread it evenly. Juices will thicken as the pie bakes and cools.

Add the crumble: Crumble the remaining dough over the blueberries in pea-sized clusters. Leave some gaps so steam can escape.

Bake: Bake for 30–38 minutes, until the crumble is golden and the filling is bubbling around the edges. If the top browns too quickly, tent loosely with foil.

Cool for clean slices: Let the pie cool at least 45–60 minutes. The filling sets as it cools, giving you tidy slices.

Serve: Enjoy warm or at room temperature. Add a spoonful of lightly sweetened whipped cream for a classic finish.