In a food processor, pulse the almond flour, flour, salt, and baking powder together. Add the butter and pulse until the mixture looks like coarse cornmeal. With the motor running, add just enough ice water through the feed tube so that the dough forms into a loose ball. Gather the dough into a ball and cover it with plastic wrap. Let it rest for 1 full hour or overnight in the refrigerator.
Preheat the oven to 400°F.
Prepare the Blueberries:
In a large bowl mix the blueberries, cornstarch, lime, and sugar until thoroughly combined.
Assemble the Galette:
On a floured work surface with a floured pin, roll the dough out to a 12-inch circle. Pile the blueberry mixture into the center 8 inches. Fold the edges of the dough over towards the center. Bake until the crust is golden brown, 15 to 20 minutes.
Let it cool for 20 to 30 minutes.
Serve with a scoop of vanilla bean ice cream or whipped cream.
TIP: Be careful not to overmix the dough or else the crust will be tough. Gluten acts like a muscle—the more you work, the harder it gets. Similarly, when you let the dough rest, it will become softer.