I love rhubarb, and this is one pie I enjoy making every Summer! Serve as is, or with whipped cream or vanilla ice cream. (Before making the pie, be sure to read the "Note" following the instructions.)
Remove both pie crusts from the package. Leave pie crusts in plastic wrap, and let sit on your kitchen counter for 15-20 minutes before using.
Meanwhile, in a large bowl, combine the flour and the 1-1/4 cups granulated sugar.
Add the rhubarb and crushed pineapple; stir until the rhubarb and pineapple is thoroughly mixed into the flour/sugar mixture. Set bowl aside.
Remove one of the pie crusts from the plastic wrap. Unroll the pie crust, and place it on a sheet of wax paper. Sprinkle the teaspoon of flour over the crust. Using your hand, lightly spread the flour over the entire crust. Place the pie crust, floured side down, inside a 9-inch pie pan.
Pour the rhubarb and pineapple mixture into the pie crust.
Remove the other pie crust from the plastic wrap. Unroll, then place over the pie filling. (I rolled out the pie crust on to the sheet of wax paper. I then took a mini cookie cutter, a star shaped cookie cutter, then cut-out and removed some of the dough near the center of the pie crust.)
Trim crust (if need be), seal and flute the edges.
Cut slits in the top of the pastry crust.
Sprinkle the top of crust with the 1-1/2 teaspoons of sugar.
(Before I bake the pie in the oven, I place (and bake) the pie pan on a 14-inch pizza tin, then place a pie shield on top the pie. I keep the pie shield on the entire time the pie is baking. This helps to prevent the edges of the crust from becoming too brown, or perhaps burnt.)
Bake the pie in a preheated 350º oven for about 55 minutes, or until the pie crust is brown on top, and the fruit juices begin to bubble out of the slits in the pie crust.
Note: I wanted to let members of this site know... that I have also made this pie using 2 (8 ounce) cans of crushed pineapple (drained well), and in place of the 15.25 ounce can, plus I also stirred 4 level tablespoons of ground flaxseed into the flour/sugar mixture before adding the rhubarb and pineapple. The pie tasted great, and I think the flaxseed helped to thicken the filling within the pie. Also, after the pie is made and cooled, I don't refrigerate it or any of the leftovers. I leave the pie set at room temperature, and cover it with paper towels. It keeps well on the kitchen counter for up to 2 days.