In a mixing bowl, combine flour and salt. Cut in the cold butter until the mixture resembles coarse crumbs.

Stir in ice water, a tablespoon at a time, until the dough comes together. Divide into two balls, flatten into disks, wrap in plastic, and refrigerate for at least 30 minutes.

In a large bowl, combine strawberries, rhubarb, sugar, flour, lemon juice, and vanilla extract. Mix well and let sit for 15 minutes.

Preheat the oven to 425?F (220?C). Roll out one disk of dough on a floured surface to fit the pie dish. Place it in the dish.

Pour the filling into the crust and dot with butter. Roll out the second disk of dough and place it over the filling. Seal and flute the edges. Cut slits in the top crust for steam to escape.

Place the pie on a baking sheet and bake for 15 minutes. Reduce the temperature to 350?F (175?C) and bake for an additional 30 minutes, or until the filling is bubbly and the crust is golden brown.

Let the pie cool for at least 2 hours before serving to allow the filling to set.