Double crust pie dough (or your preferred pie crust)
2 red plums, halved and pitted
6 cups pitted, halved sweet cherries (or 6 cups pitted frozen cherries), divided
½ cup sugar
Pinch of salt
1 tbsp. freshly squeezed lemon juice
2 tbsp. instant tapioca, ground
Pinch of ground cinnamon
2 tbsp. unsalted butter, cut into ¼-inch pieces
1 large egg lightly beaten with 1 tsp. water
step 1: Show Images
To make the filling, process the plums and 1 cup of the cherries in a food processor or blender until smooth, about 1 minute. Strain the the puree through a fine mesh strainer into a large bowl, pressing on the solids to extract as much liquid as possible; discard the solids. Add the remaining cherries, sugar, salt, lemon juice, tapioca and cinnamon to the bowl. Mix well to combine; let stand for 15 minutes.
step 2: Show Images
Preheat the oven to 400˚ F and place a baking sheet on an oven rack. Line a 9-inch pie plate with a round of pie dough. Transfer the cherry mixture to the dough-lined pie plate. Scatter the butter pieces evenly over the fruit. Top with the second round of pie dough. Pinch the edges of the dough together in a fluted pattern. Brush the top evenly with the egg wash. Using a sharp paring knife, cut 8 evenly spaced slits in the top crust to allow steam to escape. Place the pie in the freezer for 20 minutes.
step 3: Show Images
Place the pie on the preheated baking sheet and bake for 30 minutes. Lower the oven temperature to 350˚ F and continue baking about 30-40 minutes more, until the crust is golden brown and the juices are bubbling. Transfer to a wire rack and let cool to room temperature so the filling has time to set up and thicken, 2-3 hours. Slice and serve.