01 - Preheat oven to 350°F. Grease a 9x13-inch baking dish with cooking spray or butter.
02 - Spread fresh or frozen blueberries and blueberry pie filling evenly across the bottom of the prepared dish. Sprinkle lemon zest over the fruit and drizzle with lemon juice.
03 - In a medium bowl, beat softened cream cheese, granulated sugar, egg, and vanilla extract until completely smooth and creamy, about 2 minutes.
04 - Drop spoonfuls of the cream cheese mixture over the blueberry layer. Gently spread to create an even layer, taking care not to fully mix the two layers together.
05 - Evenly sprinkle the lemon cake mix over the entire surface, covering all areas.
06 - Drizzle melted butter evenly across the cake mix, ensuring most of the dry surface is moistened.
07 - Bake for 40 to 45 minutes, or until the top is lightly golden brown and the edges are bubbling.
08 - Let the cake cool for 15 minutes before serving. Serve warm or at room temperature, optionally topped with whipped cream or vanilla ice cream.