Make the Crust: In a large bowl, whisk together the gluten-free flour blend, sugar, and salt.
1 1/2 cups gluten-free all purpose flour, 1 Tablespoons granulated sugar, 1/4 teaspoon kosher salt
Add the cold cubed butter and toss it in the flour until each piece is coated. Using a pastry cutter or two forks to cut the butter into the dry ingredients until all flour is coated and the butter is the size of a pea. Some larger chunks of butter are okay. You can press and flatten them with your fingers.
1/2 cup 1 stick, unsalted butter, cubed
Add the cold water and mix well with a fork or rubber spatula until the dough starts coming together. The dough will seem dry, that’s okay. Don’t add any more water.
1/4 cup cold water
Turn the pie dough out onto a lightly floured work surface. Use floured hands to fold the dough into itself until the flour is fully incorporated into the fats and it starts to form a dough. Form it into a ball and flatten it into a 1-inch thick disc. Wrap it tightly in plastic wrap and refrigerate for at least 2 hours or up to 5 days.
Make the Filling: In a large skillet or dutch oven, stir the apple slices, sugar, brown sugar, gluten-free flour, lemon juice, cinnamon, and nutmeg together until thoroughly combined. Cover and cook on the stove over medium-low heat for 10-12 minutes, stirring frequently, until the apples begin to soften. Remove from heat and stir in the vanilla extract. Allow it to cool slightly. You can spread it out onto a large-rimmed sheet pan and place in the fridge or freezer to speed this up.
12 cups apples peeled and sliced into 1/4-inch pieces, 1/2 cup granulated sugar, 1/4 cup light brown sugar, 1/4 cup gluten-free flour, 1 Tablespoon lemon juice, 1 1/2 teaspoon cinnamon, 1/2 teaspoon nutmeg, 1 teaspoon vanilla
Make the Crumb Topping: In a medium bowl, combine the sugar, brown sugar, cinnamon, salt, and gluten-free flour. Using a silicone spatula, stir in the butter. The crumble topping will be thick and crumbly.
1/3 cup granulated sugar, 1/2 cup light brown sugar, 1 teaspoon cinnamon, 1/4 teaspoon salt, 1 1/2 cups gluten-free flour, 3/4 cup unsalted butter melted
Preheat oven to 400°F (204°C) and place a large sheet pan inside while it preheats.
Roll out the chilled dough on a well-floured work surface. Roll the dough 2-3 times then turn it a quarter until you have a 12-inch circle about 1/4-inch thick. Carefully place the dough into a 9-inch pie dish that’s 1.5- 2 inches deep. Trim off the edges and flute or tuck the dough in with your fingers, making sure it's smooth.
Spoon the filling into the crust. Pile them high, and pack it down tightly together. Sprinkle the crumb topping over apples.
Remove the baking sheet from the oven and place the pie on it and bake for 20 minutes. Keeping the pie in the oven, turn the temperature down to 375°F and cover the pie crust with a pie shield or foil around the edge. Continue to bake at 375 for 30-35 minutes, until the top is golden brown.
Allow the pie to cool for 3 full hours at room temperature before serving. Cover and store at room temperature for up to 1 day or in the fridge for up to 3 days before serving. Serve room temperature or reheat at 350 for 15 minutes before serving.