01 - Set oven temperature to 400°F (200°C).
02 - Fit the unbaked pie crust into a 9-inch pie pan and crimp the edges.
03 - Pour 1 1/2 cups water evenly over the pie crust.
04 - In a mixing bowl, blend together the granulated sugar and all-purpose flour until uniform.
05 - Sprinkle the sugar-flour mixture evenly across the surface of the water inside the crust.
06 - Drizzle vanilla extract over the filling and add a pinch of salt.
07 - Slice the unsalted butter into thin pats and distribute evenly over the top.
08 - Transfer the pie to the bottom rack in the oven. Bake for 30 minutes at 400°F (200°C).
09 - Lower oven temperature to 375°F (190°C) and bake for 20 minutes, until the crust turns golden and the filling barely jiggles.
10 - Remove the pie from the oven and cool to room temperature. Refrigerate for at least 2 hours before slicing for optimal texture.