01 - Set oven to 400°F and allow to preheat fully for even baking.
02 - Fit the unbaked pie crust into a 9-inch pie pan, crimping edges neatly.
03 - Pour 1 1/2 cups water directly into the prepared pie crust.
04 - Combine granulated sugar and all-purpose flour in a mixing bowl, then sprinkle evenly over the water in the crust.
05 - Drizzle vanilla extract over the filling and add a pinch of salt.
06 - Slice unsalted butter into thin pats and distribute across the surface.
07 - Place pie pan on the lower oven rack. Bake for 30 minutes at 400°F.
08 - Reduce oven temperature to 375°F and bake for 20 additional minutes until crust is golden and filling is set but slightly wobbly in center.
09 - Remove from oven and allow pie to reach room temperature. Refrigerate a minimum of 2 hours for easier slicing and optimal texture.