Make the pie crust: In a large bowl, whisk together flour and salt. Cut in cold butter using a pastry blender or your fingers until the mixture resembles coarse crumbs. Gradually add ice water, mixing until the dough just comes together. Wrap in plastic wrap and chill for at least 30 minutes.

Roll out the dough and fit it into a 9-inch pie plate. Trim and crimp the edges.

Make the filling: In a large bowl, combine black raspberries, sugar, cornstarch, and lemon juice. Mix well.

Pour the filling into the prepared pie crust.

Make the crumble topping: In a medium bowl, combine flour, brown sugar, cold butter, and oatmeal. Use your fingers to rub the butter into the dry ingredients until the mixture is crumbly.

Sprinkle the crumble topping evenly over the pie filling.

Bake in a preheated oven at 375°F (190°C) for 45-50 minutes, or until the crust is golden brown and the filling is bubbly. Let cool completely before serving.