In a mixing bowl, combine rhubarb, sugar, flour, and lemon juice. Set aside.
In another bowl, combine flour and salt for the crust. Cut in shortening until mixture resembles coarse crumbs. Gradually add cold water, tossing with a fork until dough forms a ball.
Divide dough in half. Roll out one half to fit a 9-inch pie dish. Transfer dough to pie dish. Trim even with edge.
Add rhubarb filling to crust. Dot with butter.
Roll out remaining dough to fit top of pie. Place over filling. Trim, seal, and flute edges. Cut slits in top.
Bake for 15 minutes. Reduce oven temperature to 350°F (175°C) and bake for 40-45 minutes longer or until crust is golden and filling is bubbly.