Delicious pie with only the freshest, ripest rhubarb.
Turn the oven up to 450 F.
Place the first crust layer over a pie plate. Combine the sugar and flour, then sprinkle 1/4 of it over the layer. Heap the chopped rhubarb over that, then sprinkle it with the remaining sugar and flour. Dot the mixture with small pieces of butter, then top it off with the second crust layer.
Bake the pie in the oven on the low rack for 15 minutes. Turn the oven down to 350 F, and continue baking for 40 to 45 minutes. Serve it right away, or put it in the fridge and serve it chilled.