Place your butter in a medium bowl and soften your butter in the microwave for about 30 seconds.
Add the almond flour, arrowroot four, and salt to the bowl and fold together.
Place a piece of parchment paper on your counter and dust it with arrowroot flour.
Transfer the dough to the parchment paper. Dust it with arrowroot flour and roll it in an oval, about 1/4 inch thick. Continue to dust with arrowroot flour as needed.
Add your berries in a bowl along with 1 tablespoon of the powdered sugar. Toss to coat the berries.
Place the berries into the center of crust.
Use the parchment paper to fold the edges into the perimeter of the galette, leaving the the center berries open.
Beat an egg in a small bowl and brush it onto the edges of the crust.
Bake for 15 minutes until the crust is golden brown.
Sprinkle with remaining tablespoon of powdered sugar and add a scoop of ice cream or whipped cream if desired!