Preheat OvenPreheat the oven to 450°F (225°C).
Prepare FillingIn a large saucepan, combine water, sugar, flour, salt, vanilla, butter, lemon juice, and raisins. Simmer for 10 minutes, stirring frequently.
Assemble PiePour the raisin filling into one pie shell. Cover with the second pie shell, seal edges, and cut steam vents.
BakeBake at 450°F (225°C) for 15 minutes, then reduce heat to 350°F (175°C) and bake for an additional 25-30 minutes.
Cool and ServeLet the pie cool before slicing. Serve warm or at room temperature.