**Prepare the pie crust**
Roll out the pie crust and fit it into a 9-inch pie pan. Trim and crimp the edges as desired. Refrigerate the crust while preparing the filling and topping.
**Make the apple filling**
In a large mixing bowl, combine the sliced apples, granulated sugar, flour, cinnamon, nutmeg, and lemon juice. Toss until the apples are evenly coated.
**Prepare the streusel topping**
In a separate bowl, mix the flour and brown sugar. Cut in the cold butter using a pastry cutter or fork until the mixture resembles coarse crumbs.
**Assemble the pie**
Preheat your oven to 375°F (190°C). Pour the apple filling into the prepared pie crust, spreading it out evenly. Sprinkle the streusel topping over the apples, covering them completely.
**Bake**
Place the pie on a baking sheet to catch any drips and bake for 50–60 minutes, or until the topping is golden brown and the filling is bubbling. Cover the edges of the crust with foil or a pie shield if they brown too quickly.
**Cool and serve**
Let the pie cool for at least 2 hours before slicing to allow the filling to set. Serve warm or at room temperature with a scoop of vanilla ice cream or whipped cream.