Preheat the oven to 375 degrees F. Line a sheet pan with parchment paper.
Toss the rhubarb, strawberries, sugar, and orange zest together in a large bowl. In a measuring cup, dissolve the cornstarch in the orange juice and then mix it in with the fruit.
Carefully ease one pie crust into a 9-inch pie plate, making sure not to stretch the dough at all, or it will shrink as the pie bakes. Spoon the fruit mixture into the pie shell, scraping the bowl with a rubber spatula to be sure you have all the juices.
For the lattice, place the second crust on a cutting surface and slice 8 equal size strips of dough with a pizza wheel. Starting at one edge, using every other strip of dough, place 5 parallel strips across the pie. Fold back the 2 strips that are on either side of the center half way and place a strip of dough across the center of the pie perpendicular to the other strips. Place the 2 strips back over the pie again and fold the 3 alternate strips half way back. Place a second perpendicular strip of dough over the pie. Place the 3 strips back over the pie again and repeat with a third strip of dough on the opposite side.
Trim the lattice pieces. Lift the edge of the bottom crust over the edge of the lattice pieces and crimp the two together with your fingers. Brush the lattice pieces with the egg wash.
Place the pie on the prepared sheet pan and place it in the middle of the oven. Lower the heat to 350 degrees F and bake 45 minutes, until the filling is very bubbly and the crust is nicely browned. Allow to cool and serve warm or at room temperature.
Perfect Pie Crust:
Yield:Makes two 9- to 11-inch crusts
Cut the butter in 1/2-inch dice and return it to the refrigerator while you prepare the flour mixture. Place the flour, sugar, and salt in the bowl of a food processor fitted with a steel blade and pulse a few times to mix. Add the butter and shortening. Pulse 8 to 12 times, until the butter is the size of peas. With the machine running, pour the ice water down the feed tube and pulse the machine until the dough begins to form a ball. Dump out onto a floured board and roll into a ball. Wrap in plastic wrap and refrigerate for 30 minutes.
Cut the dough in half. Roll each piece on a well-floured board into a circle at least 1 inch larger than the pie pan, rolling from the center to the edge, turning and flouring the dough so it doesnt stick to the board. (You should see bits of butter in the dough.) Fold the dough in half, ease it into the pie pan without stretching at all, and unfold to fit the pan. With a small sharp paring knife, cut the dough 1 inch larger around than the pan. Fold the edge under and crimp the edge with either your fingers or the tines of a fork.
"Barefoot Contessa Foolproof" by Ina Garten (c) Clarkson Potter 2012. Provided courtesy of Ina Garten. All rights reserved.