Preheat oven to 350° Fahrenheit.
Make the keto pie crust by mixing together the almond flour, coconut flour, xanthan gum, and kosher salt in a large bowl.
Add in the cold unsalted butter and use either a pastry cutter or the back of a fork to cut the butter into the flour until a crumbly mixture forms.
Pour in the beaten egg and mix until a dough comes together, then transfer to a pie pan and spread into the pan. Freeze crust for at least 10 minutes, then par-bake in the oven for 10 minutes.
Make the keto pecan filling by melting butter in a large saucepan over medium heat, then adding in the brown sugar Swerve. Whisk until Swerve has fully dissolved, then remove from heat.
Let filling cool for at least 10 minutes before whisking in the vanilla extract, salt, and eggs. Once combined, add in half of the pecan halves and pour into the par-baked pie crust.
Top with remaining pecan halves in a circular pattern, then bake for 40-45 minutes. Remove pie from oven and let cool for at least an hour before slicing and serving.