1 recipe double-crust pie dough of your choice (I use this recipe)
3 1/2 cups (about 1 1/2 pounds, untrimmed) rhubarb, stripped of any rough outer fibers and cut in 1/2-inch thick slices
3 1/2 cups (about 1 pound) strawberries, hulled and sliced or halved depending on their size
1/2 cup granulated sugar
1/4 cup light brown sugar
1 tablespoon lemon juice
1/4 teaspoon salt
1/4 cup quick-cooking tapioca
2 tablespoons unsalted butter, cut into small pieces
1 large egg yolk beaten with 1 teaspoon water (for glaze)
Preheat oven to 400 degrees. Roll out half of the pie dough on a well-floured surface to a 12 inch circle. Transfer to a 9 inch pie plate.
Combine rhubarb, strawberries, sugars, lemon, salt, and tapioca in a large bowl. Stir gently until strawberries and rhubarb are evenly coated. Place filling inside the bottom pie crust. Dot with unsalted butter.
Roll out the remaining pie dough to an 11-inch circle and cut slits to vent (or use decorative cutters or a lattice top). Transfer to top the pie filling. Trim the top and bottom dough to leave a 1/2 inch overhang over the lip of the pie plate. Fold rim of dough underneath itself to seal and then crimp the edges.
Transfer the pie to a baking sheet and brush with the egg yolk/water mixture. Bake for 20 minutes at 400, then reduce to 350 and bake an additional 25-30 minutes, until the pie is golden and the juices are bubbly.
Transfer the pie to wire rack to cool for 1-2 hours. When cool, the juices will gel. This pie will keep at room temp for up to three days.
Adapted from Smitten Kitchen.