01 - Preheat oven to 400°F (200°C).
02 - Line a 9-inch pie pan with the unbaked pie crust, crimping the edges as preferred.
03 - Pour 1 1/2 cups water directly into the prepared pie crust.
04 - In a mixing bowl, blend the granulated sugar and all-purpose flour. Sprinkle evenly over the water in the pie crust.
05 - Drizzle vanilla extract across the surface and add a pinch of salt.
06 - Slice unsalted butter into thin pats and arrange evenly atop the filling.
07 - Place the pie on the lower rack of the oven. Bake for 30 minutes at 400°F (200°C).
08 - Lower oven temperature to 375°F (190°C). Continue baking for 20 minutes, until the crust turns golden and the filling is set with a slight jiggle in the center.
09 - Remove the pie from the oven and cool completely to room temperature. Refrigerate at least 2 hours for optimal slicing and texture.