Heat the oven to 350°F and spread the blueberry pie filling in a 9-by-13-inch baking dish.

Distribute the frozen blueberries over the filling and cover them with dry lemon cake mix.

Break up all mix lumps and drizzle melted butter across the entire surface without stirring.

Bake for 48 to 52 minutes until blueberry filling bubbles through a browned crust.

Cool 30 minutes so the filling can thicken.