For a softer filling, omit the egg.
Prepare 3 cups rhubarb, cut into pieces
Mix 1 cup sugar, 2 tablespoons flour, 1 egg
Add to the rhubarb
Line a 9-inch pie pan with plain pastry. Spoon in the filling. Put on a top crust or a lattice top.
Bake at 450º about 40 minutes.