step 1 

Cut the butter into 1/2 inch pieces and set them on a plate. Place in the freezer for 10 to 15 minutes so the butter gets very, very cold.

step 2 

In a small bowl, combine ice water, vodka, sour cream, and vinegar. Whisk until well incorporated. Place in the fridge until ready to use.

step 3 

Add the flour, coconut sugar, salt, and xanthan gum to a food processor and pulse a few times to combine. Add the very cold butter and pulse until there are large pea sized chunks of butter visible.

step 4 

Pour the cold sour cream mixture over the flour mixture and pulse until the dough comes together in large pieces, about 20 seconds.

step 5 

Place dough onto a sheet of plastic wrap and form into a disk. Wrap tightly in plastic wrap and refrigerate for at least 1 hour or up to 2 days. When ready to roll out the dough, place on the counter to soften slightly.

step 6 

Once the dough has chilled for at least 1 hour, place dough between two pieces of plastic wrap and roll into a 13-inch circle. Remove the top piece of plastic wrap and gently invert dough into a 10-inch skillet, carefully pressing into place. Remove remaining plastic wrap and trim dough level with the top edge of the skillet. Cover the pie crust loosely with plastic wrap and place in the fridge for about 30 minutes.

step 7 

Preheat oven to 375 degrees. Bake chilled pie crust until crisp and golden brown, about 25 to 35 minutes. Remove crust from oven and let cool slightly before filling.

step 8 

Place a large dutch oven over medium heat. Add the sliced apples, maple syrup, coconut sugar, lemon zest, salt, and cinnamon, stir well to combine. Cover and cook, stirring often, until apples are fork-tender but still hold their shape, about 15 to 20 minutes. Transfer cooked apples to a rimmed baking sheet and let cool for at least 30 minutes. Drain and discard liquid from apples using a colander, set apples aside.

step 9

In the bowl of a food processor, add the oat flour, coconut sugar, cinnamon, and salt. Pulse a few times to combine. Add the butter and pulse until the mixture looks like coarse meal, and no large pieces of butter are visible. Add the walnuts and pulse a few more times until the nuts are broken down a bit and the mixture begins to clump together. Cover and place in the fridge until ready to use.

step 10

Preheat oven to 400 degrees. Place cooked apples into slightly cooled pie shell and press into an even layer. Crumble the topping evenly over the apples, pinching into 1/4 to 1/2 inch pieces. Bake until the top is golden brown and crisp, about 25 to 35 minutes.

step 11 

Let pie cool on a wire rack for 2 hours before serving.