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