Combine flour and salt in a large bowl. Cut in butter with a pastry blender or two knives until mixture resembles coarse crumbs with some pea-sized pieces.
Combine water and vodka in a measuring cup and add to flour mixture. Stir to form a shaggy dough. Turn dough out onto a lightly floured surface and bring it together. Wrap in plastic, form into a disk and refrigerate for an hour.
On a lightly floured surface, roll pastry into a 13-inch (33cm) round. Place it in a deep 9-inch (23cm) pie plate. Trim and crimp the edges. Refrigerate for 20 minutes.
Heat oven to 400F (205C).
Whisk together filling ingredients in a large bowl. Pour into shell. Bake for 10 minutes, reduce the heat to 350F (176C) and continue to bake until the middle is just set, about 1 hour. Tent with foil if pie begins to brown.
Transfer pie to wire cooling rack to cool completely. Serve topped with whipped cream and sprinkled with cinnamon.