In a medium bowl, whisk together the flour, 2 tablespoons of sugar, and salt.
Using a pastry blender or two knives, cut the butter into the flour mixture until it resembles coarse crumbs.
Add the ice water and mix until the dough comes together. Gently knead the dough until it is smooth. Wrap in plastic wrap and refrigerate for 30 minutes.
In a large bowl, combine the rhubarb, strawberries, 1/2 cup sugar, cornstarch, and orange zest. Stir to combine.
Roll out the dough on a lightly floured surface into a 12-inch circle. Place the dough in a 9-inch pie plate.
Pour the fruit mixture into the pie plate and spread evenly. Dot with the 2 tablespoons of butter.
Roll out the remaining dough into a 12-inch circle. Place on top of the fruit mixture and crimp the edges together.
Brush the top of the crust with the beaten egg and sprinkle with the coarse sugar.
Bake for 45 minutes, or until the crust is golden brown and the filling is bubbling.
Cool on a wire rack before serving.
Interesting Facts
Strawberries are actually a member of the rose family.
Rhubarb is one of the oldest vegetables known to mankind.
Orange zest can be used to add a burst of flavor to any dish.