Make the Pie Crust: In a large bowl, whisk together the flour and salt. Cut in the cold butter using a pastry blender or your fingers until the mixture resembles coarse crumbs. Gradually add the ice water, one tablespoon at a time, mixing until the dough just comes together. Form the dough into a disk, wrap it in plastic wrap, and refrigerate for at least 30 minutes.

Prepare the Apple Filling: In a large bowl, combine the sliced apples, granulated sugar, flour, cinnamon, nutmeg, and lemon juice. Toss gently to ensure all the apple slices are evenly coated.

Make the Streusel Topping: In a medium bowl, combine the flour, brown sugar, oats, and cinnamon. Cut in the cold butter using a pastry blender or your fingers until the mixture forms coarse crumbs. Place in the refrigerator until ready to assemble the pie.

Roll Out the Crust: On a lightly floured surface, roll out the chilled pie crust into a 12-inch circle. Carefully transfer the crust to a 9-inch pie plate. Trim any excess dough and crimp the edges to create a decorative border.

Assemble the Pie: Pour the apple filling into the prepared pie crust, distributing the apples evenly. Sprinkle the streusel topping generously over the apple filling, covering the entire surface.

Bake the Pie: Preheat your oven to 375°F (190°C). Bake the Dutch Apple Pie with Streusel Topping for 45-55 minutes, or until the crust is golden brown and the streusel topping is nicely browned. If the crust starts to brown too quickly, you can cover the edges with foil or use a pie shield.

Cool and Serve: Let the pie cool completely on a wire rack before slicing and serving. This allows the filling to set properly.