01 - Preheat oven to 350°F. Line a 9x13-inch baking pan with parchment paper or grease lightly.
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 the crust layer.
04 - Beat cream cheese until smooth. Add eggs one at a time, then mix in powdered sugar, lemon juice, lemon zest, and vanilla until fluffy and well combined.
05 - Pour lemon mixture over base and spread evenly. Bake 35-40 minutes until edges are set but center remains slightly jiggly.
06 - Let cool completely before cutting into squares. Dust with powdered sugar if desired.