Preheat your oven to 350°F (175°C).
Pour both cans of blueberry pie filling into the 9×13 inch baking dish and spread them into an even layer using a rubber spatula.
Sprinkle the dry cake mix evenly over the layer of blueberry filling; do not mix it in, as the powder needs to sit on top to create the crust.
Distribute the thin slices of cold butter evenly across the surface of the dry cake mix, ensuring as much of the dry powder is covered as possible.
Sprinkle the fresh lemon zest over the top of the butter and cake mix.
Bake for 45 to 50 minutes, or until the top is golden brown and the fruit filling is bubbling vigorously around the edges.
Remove from the oven and let the dessert sit for at least 10 minutes before serving to allow the fruit layer to thicken slightly.