Preheat oven to 375 degrees F (190 C). 

Combine cherries, blueberries, sugar, flour, and lemon juice in a large mixing bowl and stir to combine. 

Roll out pie crust to a 12-inch round. Put dough on top of parchment paper on a cookie sheet. 

Mound cherries and blueberries in the center of the pie crust, leaving 2 inches of border. 

Fold edges up over and slightly overlap dough on itself. 

Beat egg in a small bowl and brush on dough edges. 

Bake for 40 to 50 minutes or until golden brown. 

Let cool for 10 minutes before cutting.