In a small bowl, whisk together the egg, chilled water, and apple cider vinegar until well combined.

In a larger bowl, combine the gluten-free flour blend, sugar, xanthan gum, baking powder, and salt, stirring thoroughly.

Add the cubed cold butter to the flour mixture and work it in until it resembles coarse crumbs.

Pour the wet mixture into the dry ingredients and stir until a dough forms, adding more chilled water as needed.

Shape the dough into a disk, wrap in plastic wrap, and refrigerate for at least 30 minutes.

Roll the chilled dough on parchment paper into a 13-inch round, about ¼ inch thick.

Transfer the rolled dough to a 9-inch pie dish and press it in, crimping the edges as desired.

Pre-bake the crust at 350°F for about 10 minutes or until edges are lightly golden, as per your recipe instructions.