01 - Preheat oven to 350°F. Grease a 9x13-inch baking dish thoroughly with butter or cooking spray.
02 - Spread fresh or frozen blueberries and blueberry pie filling evenly across the bottom of the prepared dish. Sprinkle lemon zest over the surface and drizzle with lemon juice.
03 - In a medium bowl, beat cream cheese, granulated sugar, egg, and vanilla extract using an electric mixer or whisk until completely smooth and creamy, about 2-3 minutes.
04 - Drop spoonfuls of the cheesecake mixture over the blueberry layer. Gently spread with a spatula to create an even layer, being careful not to fully mix the two layers together.
05 - Sprinkle the lemon cake mix evenly over the entire surface, covering all areas completely.
06 - Pour melted butter evenly over the cake mix, ensuring most of the dry mix is moistened. The butter will create pockets of cake as it bakes.
07 - Bake for 40-45 minutes until the top is lightly golden brown and the edges are bubbling. The center should be set but still slightly moist.
08 - Allow the cake to cool for 15 minutes before serving. Serve warm or at room temperature, optionally topped with whipped cream, powdered sugar, or vanilla ice cream.