01 - Preheat oven to 350°F. Line a 9x13-inch baking pan with parchment paper or lightly grease with butter.
02 - Combine cake mix, melted butter, and egg in a mixing bowl. Mix until soft dough forms.
03 - Press dough evenly into bottom of prepared pan to form base layer.
04 - Beat cream cheese until smooth. Add eggs one at a time, mixing well. Mix in powdered sugar, lemon juice, lemon zest, and vanilla extract until fluffy and smooth.
05 - Pour lemon mixture over base and spread evenly. Bake for 35-40 minutes until edges are set and center is slightly jiggly.
06 - Let cake cool completely before cutting into squares. Dust with powdered sugar if desired.