in a lrg bowl, combine sugar,tapioca, salt and cinnamon. Add rhubarb an strawberries, toss gently. let stand for 20 min.
Line a 9-inch. pie plate with bottom pastry; trim pastry 1 inch beyond edge. pourbfilling into crust; dot with butter. Roll out remaining pastry; make a lattice crust. trim, seal and flute edges
Bake at 400 degrees f for 35 to 40 min or until pie shells are golden brown and the filling is bubbly. cover the edges of crust with foil the last 15 min to prevent overbrowning if necessary. Cool an serve