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 softened cream cheese, granulated sugar, egg, and vanilla extract until completely smooth and creamy, about 2 minutes.
04 - Drop spoonfuls of the cheesecake mixture over the blueberry layer. Gently spread to create an even layer without fully mixing into the fruit.
05 - Sprinkle the lemon cake mix evenly over the entire surface, ensuring complete coverage of the cheesecake layer.
06 - Drizzle melted butter evenly across the top of the cake mix, covering as much surface area as possible to moisten the dry mix.
07 - Bake for 40 to 45 minutes until the top is lightly golden brown and the edges are bubbling with fruit filling.
08 - Let the cake cool for 15 minutes before serving. Serve warm or at room temperature, topped with whipped cream or vanilla ice cream if desired.