Begin by preheating the oven to 350 degrees F to bake your sweet potatoes. Wash and dry the outside of the potatoes thoroughly, then prick with a fork multiple times. Place on a baking sheet and bake for 1 hour and 30 minutes. This time will fluctuate depending on how large your sweet potatoes are.
Meanwhile, make the crust. Combine the flour, salt, and sugar in a food processor and pulse to combine. Then, add your optional xanthan gum and butter and pulse 7-8 times until the mixture resembles coarse crumbs. Stream in the ice water one tablespoon at a time while pulsing and then shut off the machine. If the dough holds together when squeezed, it is ready.
Dump the dough out onto a clean work surface and gently knead into a rounded disk. Wrap in plastic wrap and refrigerate for 30 minutes to an hour, or until the fillings are ready.
Once chilled, roll out your dough using a rolling pin to about ⅛-inch thick. Roll the dough up the pin and place it into a buttered pie plate, unrolling the dough fully. Crimp the edges and place back in the fridge. You may need to patch some holes or tears in the dough.
Once the sweet potatoes are done, remove the skins and add the flesh to a bowl. Mash with a fork before adding the rest of the sweet potato filling ingredients. Mix to combine fully and move on to the pecan layer.
For the pecan layer, break the eggs into a small bowl and whisk. Add the rest of the ingredients and stir until homogenous.
To your cold pie shell, add the sweet potato filling a smooth out with a spatula.
Top with the pecan filling, spreading the pecans carefully and evenly across the top.
Bake in a 350-degree oven for 55-65 minutes, or until a toothpick inserted in the center comes out clean.
Allow the pie to cool completely before serving.