Preheat your oven to 375°F (190°C).
In a mixing bowl, combine flour and butter. Mix until it resembles coarse crumbs.
Add ice water gradually and mix until the dough comes together.
Roll out half of the dough and fit it into a pie dish. Refrigerate while preparing the filling.
In another bowl, combine blackberries, sugar, cornstarch, lemon juice, lemon zest, and vanilla extract.
Pour the filling into the prepared pie crust.
Roll out the remaining dough and place it over the filling. Seal and crimp the edges.
Cut a few slits in the top crust to allow steam to escape.
Bake for 45 minutes or until the crust is golden brown and the filling is bubbly.
Let the pie cool before serving.