Preheat your oven to 400°F (200°C).

On a lightly floured work surface, use a rolling pin to create a disc of pie dough to fit a 9-inch pie pan. Use this as the bottom crust. Transfer the dough to the pie pan leaving some overhang

In a large bowl, Combine the flour and sugar together and mix well

Sprinkle half of the flour/sugar mixture into the pie pan

Toss 2 cups of chopped rhubarb on top of the flour/sugar mixture

Layer one more time with the rest of the flour/sugar mixture and then the remaining 2 cups of rhubarb

Dot the top with small pieces of butter for the final layer

Roll out the bottom crust on a cutting board and place it over the filling. Trim any excess dough and crimp the edges to seal. Cut a few slits in the top crust to allow steam to escape.

Optional: Brush the top crust with milk or heavy cream and sprinkle with sugar.

Place the pie dish on a baking sheet to catch any drips and bake at 400°F for 15 minutes. After that, lower the temperature to 350°F and finish baking for another 30 minutes or until the crust is golden brown and the filling is bubbly. To avoid burning, you may want to use a pie shield to keep the edges from browning too fast. I fashioned one out of aluminum foil but you can also buy one like this.

Let the pie cool on a wire rack for at least 2 hours before serving to allow the filling to set.