In a mixing bowl, combine rhubarb, strawberries, sugar, cornstarch, and lemon juice. Set aside.
In another bowl, mix flour and butter until it resembles coarse crumbs. Gradually add ice water until dough forms.
Divide dough in half. Roll out one half and place in a pie dish. Add filling. Roll out the other half and place on top. Seal edges and cut slits for steam.
Bake for 50 minutes or until crust is golden and filling is bubbly.