In a large bowl, whisk together flour and salt. Add cold butter cubes and mix until the mixture resembles coarse crumbs.
Sprinkle ice water over the flour mixture, stirring gently until the dough comes together. Shape into a disk, wrap in plastic, and refrigerate for at least 30 minutes.
In a medium bowl, mix cranberries, sugar, cornstarch, and vanilla extract. Set aside.
On a floured surface, roll out the dough into a 12-inch circle. Transfer to a parchment-lined baking sheet.
Pile the cranberry mixture in the center of the dough, leaving a 2-inch border. Fold the edges over the filling.
Brush the edges of the dough with beaten egg and sprinkle with coarse sugar.
Bake for 40-45 minutes or until the crust is golden brown and the filling is bubbling.
Notes
For a twist, consider adding a sprinkle of cinnamon to the cranberry mixture for additional warmth.