Combine almond flour, coconut flour, arrowroot starch, sweetener, xanthan gum and salt in the bowl of a food processor. Pulse to combine.
Sprinkle surface with butter pieces and pulse until mixture resembles coarse crumbs.
With processor running on low, add ice water, one tablespoon at time until dough begins to clump together.
Place a large piece of parchment on work surface and dust liberally with additional almond flour. Turn out dough and pat into a circle. Sprinkle with more almond flour and cover with another large piece of parchment.
Roll out carefully into an 11-inch circle. Remove top layer of parchment. Place a 9-inch pie pan upside down on crust and then carefully flip both over so crust is lying in the pie pan. Remove parchment. (Alternatively, you can skip rolling out the pastry and simply press the crust into the bottom and up the sides of the pan).
You may get some cracking and tears. Simply use small pieces of pastry from the overhang to patch them up. Crimp the edges of the crust and prick all over with a fork.
Bake crust 12 minutes, then remove and let cool.
In a medium saucepan over medium heat, combine 1 cup of the water, sweetener, lemon zest and salt. Bring to just a boil, whisking frequently, until sweetener dissolves.
In a medium bowl, whisk egg yolks until smooth. Slowly add about ½ cup of the water to the egg yolks, whisking constantly. Then gradually whisk the egg yolks back into the pan and lower the heat to low. Cook for 1 minute more, stirring continuously.
Stir in lemon juice and butter and whisk until smooth. Sprinkle surface with xanthan gum and whisk vigorously to combine.
In a small bowl, stir together the remaining two tablespoons of water and the gelatin. Let sit 2 minutes until gelled, then stir into hot lemon mixture, whisking until well combined. Cover and set aside while making the meringue.
In a large bowl, beat egg whites with cream of tartar and salt until frothy. With beaters going, slowly add sweeteners and vanilla extract and continue to beat until stiff peaks form.
Preheat oven to 300F.
Pour warm filling into crust. Dollop with meringue and spread right to the edges so that the meringue meets the crust. Swirl the top with the back of a spoon.
Bake 20 minutes or until meringue topping is golden and just barely firm to the touch. Remove and let pie cool 20 minutes, then refrigerate at least 3 hours to set.
Serves 10. Each serving has 7.22 g of carbs and 2.12 g of fiber. Total NET CARBS = 5.1 g.Food energy: 218kcal Total fat: 17.51g Calories from fat: 157 Cholesterol: 98mg Carbohydrate: 7.22g Total dietary fiber: 2.12g Protein: 6.45g Sodium: 174mg