Prepare a double pie crust according to separate instructions. Chill for at least one hour.
Rinse blueberries and set aside to dry.
Chop rhubarb into 1/4 inch slices.
Roll out the bottom pie crust. Place in a 9-inch pie plate and refrigerate while you make the filling.
Combine blueberries, rhubarb, maple syrup, lemon juice, and lemon zest in a large mixing bowl.
Add the dry ingredients (flour, cornstarch, and salt) and stir until everything is combined and no clumps of dry ingredients remain.
Spoon the filling into the chilled bottom crust.
Arrange the top crust with the design of your choice and crimp edges to seal.
Place pie back in the fridge for 15-20 minutes while you preheat the oven to 425°F.
Transfer chilled pie to a rimmed baking sheet, then bake at 425°F for 25 minutes.
Reduce temperature to 350ºF and bake for 30 more minutes.
Add a crust shield and continue to bake for an additional 15-20 minutes or until filling is bubbly.