Preheat oven to 450°F. Move rack to lowest position in the oven.
In a bowl, combine flour and sugar. Set aside.
Roll out half of the pastry and place in a 9-inch pie plate. Chill the bottom crust while you roll out the top crust.
After rolling the pastry for the top crust, remove bottom crust from the refrigerator. Sprinkle 1/3 of the flour-sugar mixture over the bottom crust. Pile the chopped rhubarb on top of the flour-sugar. Sprinkle the remaining sugar mixture over the rhubarb. Top with the pastry for the top crust. Trim and crimp/flute the edges.
Set pie on a baking sheet. Bake on the lowest rack for 15 minutes. Reduce oven temperature to 350°F and bake for an additional 40-45 minutes or until crust is golden and the juices are bubbly.
Notes
If you are making this pie with frozen rhubarb, do not thaw the rhubarb first. Add it to the pie while it is still frozen.Check the pie after about 30 minutes to make sure the edges of the crust are not browning too quickly. If you find that they are, you can cover them lightly with foil or a pie crust shield.Makes 1 9-inch pie.Slight adapted from allrecipes.