Rhubarb Custard Pie

2-9 inch pie crusts
1 C sugar
2 large eggs
2 T all-purpose flour
1/2 tsp salt
1 lb rhubarb, trimmed, halved lengthwise, and chopped (about 4 cups)

On lightly floured surface, roll one dough round into 12-inch circle. Transfer to 9-inch pie plate, cover with plastic wrap, and refrigerate 30 minutes. Roll second dough into 12-inch circle and refrigerate, covered, on large plate for 30 minutes.  Adjust oven rack to lowest position and heat oven to 375 degrees. Whisk sugar, eggs, flour, and salt in large bowl. Stir in rhubarb. Scrape filling into prepared pie shell. Brush border of dough with water, then arrange top crust over filling. Crimp edges of pie. Cut four 1-inch slits near center of pie.  Bake until juices are bubbling and crust is golden brown, about 50 minutes. Cool completely on wire rack, about four hours. Serve.