Preheat oven to 375°F (190°C).
In a mixing bowl, combine flour and salt. Cut in the butter until mixture resembles coarse crumbs. Stir in ice water, a tablespoon at a time, until mixture forms a ball. Divide dough in half, and shape into discs. Wrap in plastic wrap and refrigerate for 4 hours or overnight.
Roll out one disc of dough on a lightly floured surface to fit a 9-inch pie dish. Place crust in pie dish. Roll out the second disc for the top crust.
In a large bowl, combine blackberries, sugar, cornstarch, lemon juice, lemon zest, and vanilla extract. Pour into the pie crust.
Cover with top crust, seal edges, and cut slits in the top to allow steam to escape.
Bake in preheated oven for 45 minutes, or until crust is golden brown and filling is bubbly. Cool on a wire rack.