- ⅓ cup almond meal flour
- ⅓ cup brown rice flour
- ⅓ cup tapioca flour
- ⅓ cup potato starch
- 1 tablespoon sugar
- ½ teaspoon salt
- 3 tablespoons unsalted butter, chilled
- 3 tablespoons milk
- 2 pounds Granny Smith apples, peeled, cored, and thinly sliced
- ⅓ cup granulated sugar
- ⅓ cup packed brown sugar
- 2 tablespoons lemon juice
- 1 tablespoon cornstarch
- 1 teaspoon ground cinnamon
- ¼ teaspoon salt
- ¼ teaspoon nutmeg
- Cooking spray
- 1 tablespoon unsalted butter, chilled
- ¼ cup granulated sugar
- ¼ cup packed brown sugar
- ¼ teaspoon salt
- 1 cup gluten-free quick cooking oats
- 4 tablespoons chilled unsalted butter, cut into small cubes
Prepare the crust: In a bowl, combine flours, potato starch, sugar, and salt and stir with a whisk. Cut in the butter until mixture resembles a coarse meal. Add milk, and toss with a fork until moist. Gently press the mixture into a 4-inch circle on 2 sheets of parchment paper, cover with plastic wrap and refrigerate for at least 1 hour.
Prepare the filling: In a large bowl, combine the apples, sugar, brown sugar, lemon juice, cornstarch, ground cinnamon, salt, and nutmeg and toss. Preheat the oven to 350°F and oil or spray a 9-inch pie plate with cooking spray.
Unwrap the pie dough and, between 2 pieces of parchment paper, roll into a 12-inch circle. Remove top piece of parchment paper, place the pie plate upside down on dough and, using your hand, invert the dough into plate. Slowly peel off the parchment paper, and tuck into pie plate. Press dough against bottom and sides of the pan, folding the edges under or fluting them decoratively.
Spoon the apple filling into the pie crust, top with 1 tablespoon cubed unsalted butter, and bake for 20 minutes.
To prepare the topping, combine ¼ cup granulated sugar, ¼ cup brown sugar and ¼ teaspoon salt in a food processor and pulse until incorporated. Add the oats and butter, pulsing until coarse and crumbly.
Remove the pie from the oven and sprinkle with topping, pressing gently to adhere. Bake until golden brown, about 30 minutes. Cool on wire rack.