Make the Pie Crust (or use store-bought):

1. Mix dry ingredients: In a large bowl, whisk together flour and salt.
2. Cut in butter: Add cold cubed butter and use a pastry cutter or fork to work it into the flour until the mixture resembles coarse crumbs with pea-sized butter pieces remaining. This creates the flaky texture.
3. Add water: Drizzle in ice water, 1 tablespoon at a time, mixing gently with a fork until the dough just comes together. You may not need all the water. The dough should hold together when pressed but not be sticky.
4. Chill the dough: Form dough into a disk, wrap tightly in plastic wrap, and refrigerate for at least 30 minutes (or up to 2 days). This rest period allows the gluten to relax and the butter to firm up.
5. Roll and fit: On a lightly floured surface, roll the chilled dough into a 12-inch circle about ⅛-inch thick. Carefully transfer to a 9-inch pie dish, gently pressing into the bottom and sides. Trim excess dough, leaving a 1-inch overhang, then fold under and crimp the edges decoratively. Prick the bottom with a fork several times. Refrigerate while you prepare the filling.

Prepare the Apple Filling:

6. Preheat oven: Preheat your oven to 375°F (190°C). Place a baking sheet on the lower oven rack to catch any drips.
7. Combine apples and seasonings: In a large bowl, combine sliced apples, sugar, flour, cinnamon, nutmeg, lemon juice, and vanilla. Toss everything together until apples are evenly coated. The flour will thicken the juices as they bake.
8. Fill the crust: Arrange the apple mixture in the prepared pie crust, mounding it slightly in the center. Pack the apples in snugly—they’ll shrink as they bake. Pour any remaining juices from the bowl over the apples.

Make the Streusel Topping:

9. Mix streusel ingredients: In a medium bowl, combine flour, brown sugar, cinnamon, and salt. Add cold cubed butter and use a pastry cutter or your fingers to work it in until the mixture forms coarse, pea-sized crumbs that hold together when squeezed. You want a mix of fine crumbs and larger clumps for the best texture.
10. Add topping to pie: Sprinkle the streusel mixture evenly over the apples, covering them completely. Press down very gently to help it adhere. Don’t worry about it being perfect—rustic is beautiful!

Bake the Pie:

11. Bake: Place the pie on the preheated baking sheet in the oven and bake for 50-60 minutes. The pie is done when the streusel is golden brown, the apples are tender when pierced with a knife, and the juices are bubbling around the edges.
12. Protect the edges: If the crust edges or streusel topping start browning too quickly (usually after 30-35 minutes), cover them loosely with aluminum foil or a pie shield.
13. Cool: Remove from the oven and let cool on a wire rack for at least 2 hours before slicing. This allows the filling to set properly so slices hold their shape. The pie can be served warm or at room temperature.