Preheat oven to 375°F (190°C).
In a mixing bowl, combine flour and salt. Cut in the butter until the mixture resembles coarse crumbs. Gradually add ice water, tossing with a fork until dough holds together when pressed. Divide dough in half. Shape each into a disk; wrap and refrigerate for 1 hour or overnight.
On a lightly floured surface, roll out one portion of dough to fit a 9-inch pie dish. Transfer dough to pie dish. Trim even with edge. Add filling.
For filling, in a large bowl, combine blackberries, sugar, cornstarch, lemon juice, lemon zest, and vanilla. Toss to coat. Spoon into crust.
Roll out remaining dough to fit top of pie; place over filling. Trim, seal, and flute edges. Cut slits in top. Bake until crust is golden brown and filling is bubbly, 45-50 minutes. Cool on a wire rack.