Preheat your oven to 375°F (190°C).
In a mixing bowl, combine flour and salt. Cut in the cold butter until the mixture resembles coarse crumbs. Gradually add ice water, mixing until the dough comes together. Divide the dough in half, shape into discs, wrap in plastic, and refrigerate for at least 30 minutes.
Roll out one disc of dough on a floured surface and fit into a 9-inch pie dish. Trim the edges, leaving a 1-inch overhang.
In a large bowl, combine blackberries, sugar, cornstarch, lemon juice, and lemon zest. Pour the filling into the prepared crust.
Roll out the second disc of dough and place it over the filling. Trim, fold, and crimp the edges. Cut slits in the top crust to allow steam to escape.
Bake for 45 minutes or until the crust is golden and the filling is bubbly. Let cool before serving.