01 - Preheat oven to 350°F. Line a 9x13-inch baking pan with parchment paper or grease lightly with cooking spray.
02 - Combine yellow cake mix, melted butter, and egg in a mixing bowl. Mix until a soft, thick dough forms.
03 - Press the dough evenly across the bottom of the prepared baking pan using your hands or a spatula.
04 - Beat cream cheese until smooth and creamy. Add eggs one at a time, mixing well after each. Blend in powdered sugar, lemon juice, lemon zest, and vanilla extract until fluffy and fully incorporated.
05 - Pour the lemon cream cheese mixture over the pressed base layer and spread evenly. Bake for 35-40 minutes until edges are set and center has a slight jiggle.
06 - Let the cake cool completely in the pan before cutting into squares. Dust with additional powdered sugar if desired and serve with fresh berries or whipped cream.