Grease a 9 inch pie pan with unsalted butter.
In a large bowl, whisk together the almond flour, xanthan gum and baking powder until well combined.
Drizzle the melted butter over the flour mixture.
Using a fork, toss until the butter is evenly distributed and the mixture resembles coarse crumbs.
Gradually add the water, 1 tbsp at a time, stirring until the mixture pulls away from the sides of the bowl and starts to come together into a ball.
Transfer the dough to the prepared pie pan.
Form the quiche crust by gently pressing the dough evenly across the bottom, up the sides and onto the rim of the pan.
The dough should be uniform thickness on the bottom and sides of the crust.
Chill the crust for 30 minutes before using.
Position the oven rack in the lower third of the oven and heat the oven to 350F.
In a medium bowl, using a wire whisk, lightly beat the eggs.
Gradually whisk the milk until well combined.
Stir in the parsley, salt and pepper.
Layer the bacon and scallions in the bottom of the chilled quiche crust.
Sprinkle the cheese over the top.
Pour the egg mixture into the crust, filling nearly to the top.
Bake until the top of the crust is golden brown, the filling is set and a knife inserted in the center comes out clean, 45 minutes.
Place the pan on a wire rack and cool for 10 minutes before serving.