1. Preheat your oven to 350°F (175°C) and grease a 9×13-inch baking dish with non-stick cooking spray or butter.
2. In a large mixing bowl, combine the lemon cake mix with the melted butter and eggs. Stir the ingredients together until the mixture becomes crumbly.
3. Spread half of the crumbly cake mix evenly across the bottom of the prepared baking dish, pressing it down gently to create a solid base layer.
4. Pour the lemon pie filling or lemon curd over the cake mix base and spread it evenly to cover the entire layer.
5. In another bowl, beat the softened cream cheese, powdered sugar, and vanilla extract together until smooth and creamy.
6. Drop spoonfuls of the cream cheese mixture over the lemon filling, spacing them evenly throughout the layer.
7. Sprinkle the remaining half of the cake mix over the cream cheese mixture, creating a crumble topping for the cake.
8. Place the baking dish in the preheated oven and bake for 45-50 minutes or until the top is golden brown and the edges pull slightly away from the baking dish.
9. Remove the cake from the oven and allow it to cool slightly before serving.
10. Serve warm or at room temperature, optionally garnished with whipped cream, lemon zest, or nuts for an added layer of flavor and texture.