01 - Preheat oven to 350°F. Line a 9x13-inch baking pan with parchment paper or lightly grease with butter.
02 - Combine yellow cake mix, melted butter, and egg in a mixing bowl. Stir until a soft, cohesive dough forms.
03 - Evenly press the dough across the bottom of the prepared baking pan to create a uniform base layer.
04 - Beat softened cream cheese until completely smooth. Add eggs one at a time, mixing well after each addition. Blend in powdered sugar, lemon juice, lemon zest, and vanilla extract until the mixture is fluffy and homogeneous.
05 - Pour the lemon cream cheese mixture evenly over the prepared base. Bake for 35-40 minutes until edges are set but center remains slightly jiggly. Avoid overbaking to maintain the gooey texture.
06 - Let cool completely in the pan before cutting into squares. Optionally dust with additional powdered sugar before serving.