Prep: 1. Preheat oven to 400 degrees. 2. Slice rhubarb into 1/2" slices 3. Hull and cut strawberries into quarters. 4. Juice lemon. 5. Separate egg. Mix yolk with 1 teaspoon of water. (freeze the egg white for another use later) Make: 1. Combine rhubarb, strawberries, sugars, lemon juice, salt and tapioca. 2. Place pie dough in pie pan. 3. Pour filling into pie dough and cover with second pie crust and crimp edges together. 4. Place the pie pan on a baking sheet (in case it bubbles up) and brush with the egg yolk mixture. 5. Bake for 20 minutes then reduce temperature to 350 degrees and bake for 25 to 30 minutes more, until crust is browned. 6. Let cool for at least 2 hours to fully set.
If you want to take this recipe up a notch use our basic pie dough recipe! Using tapioca is important for this pie to set properly, if you don't want to buy it and have arrowroot powder or cornstarch on hand you can substitute them but the pie will be runnier. If you substitute one of those it becomes even more important to let the pie cool completely before serving. Depending on the sweetness of your fruit (and your personal sweet tooth) you may want to adjust the sugar to taste.