Turnbinado sugar or sugar in the rawfor sprinkling
Preheat oven to 425 degrees F.
In a large bowl, combine the flour and salt.
Add the shortening to the flour mixture in small pieces and with a pastry cutter cut the shortening in until it resembles coarse meal,
Add the ice water one tablespoon at a time, mixing well with a fork, and ONLY until the dough is moist enough and will form a ball when pressed together. You may not need to use the full 8 tablespoons of water.
Divide dough in half and form into balls, with one being slightly larger.
On a lightly floured surface or between two sheets of wax paper, roll one ball of dough out evenly from the middle so that it is approximately 2 inches larger than the pie plate. This will be the bottom crust.
Place dough gently into the pie plate by loosely rolling it up onto the rolling pin. Center the pin over the pie plate and carefully unroll.
In a medium bowl, combine rhubarb, strawberries, sugar, Minute Tapioca and orange zest. Mix well to combine. Allow to sit for 15 minutes.
Place filling into unbaked pie shell.
For Lattice Topping
On your lightly floured work surface or between two sheets of wax paper, roll the dough out to approximately 11 inches in diameter.
Cut the dough into slices 1/2 to 3/4-inch wide.
Beginning with the smaller piece of dough on the left, place it on the left side of the pie. Place every other strip of dough on top of the pie going across vertically until you reach the right side.
Fold every other strip of dough gently back over itself, refer to The Kitchn.com tutorial and YumSugar video if you have questions.
Place one of the longer remaining dough strips onto the center of the pie just next to the pieces of folded dough.
Fold the strips of dough gently over that piece just placed.
Working to the right of that strip, fold the opposite dough pieces back over themselves.
Place a slightly smaller strip close to the original, but not touching, and again gently fold the strip of dough over onto this strip.
Repeat process using gradually smaller strips and alternating between forming the over / under patter across the top of the pie.
When you have reached the side of the pie, return to the middle and begin working to the left of the original strip placed, alternating between folded strips.
Repeat process until pie is covered.
If needed, trim the edges of the pie crust.
Roll them up towards the center of the pie.
Crimp the edges so that the strips and bottom pie crust are firmly together.
In a small bowl, whisk together egg and 2 tablespoons water.
Using a pastry brush, gently brush egg wash over crust.
Sprinkle with Turnbinado or raw sugar.
Bake for 45 minutes or until bubbles form and gently burst. Transfer to a wire rack to cool before serving.