In a large bowl, combine the chopped rhubarb, strawberries, sugar, tapioca flour, orange zest, and salt. Toss everything together gently until the fruit is well coated. Let this mixture rest for 15 to 30 minutes. This resting period allows the tapioca flour to begin absorbing the juices, which helps thicken the filling.
While the filling rests, prepare your pie crust. If you’re using homemade dough, allow it to rest at room temperature for about 10 minutes. This makes rolling it out much easier. Roll out the bottom crust to about ⅛ inch thick, ensuring it’s large enough to fit your 9-inch pie plate.
Carefully line the pie plate with the rolled-out crust, making sure to trim any excess overhang. You want a little overhang to crimp later, but not too much.
Once your filling has rested, pour off any excess juice that has collected at the bottom of the bowl. This step is crucial to prevent a soggy pie.
Spoon the drained filling into the prepared crust, spreading it out evenly. Roll out the top crust, then place it over the filling. Trim the edges, crimp to seal, and cut a few small slits in the top crust to allow steam to escape. For a decorative touch, consider creating a lattice pattern with the top crust.
Brush the top crust with a beaten egg to give it a beautiful golden color once baked. This step also adds a lovely glossy finish to your pie.
Preheat your oven to 425°F (218°C). Place the pie on the bottom rack and bake for 15 minutes. This initial high temperature allows the crust to start cooking and prevents it from becoming soggy.
After 15 minutes, reduce the oven temperature to 350°F (177°C) and continue baking for an additional 45 to 60 minutes. You're looking for the crust to be deep golden, and the filling should be bubbling through the vents.
Once baked, remove the pie from the oven and let it cool completely on a wire rack for at least a couple of hours. This cooling period allows the filling to set properly, making it easier to slice.
After cooling, slice the pie and serve it to your family and friends. Watch their faces light up as they take their first bite of your delicious Strawberry Rhubarb Pie. Enjoy!