Preheat the oven to 350°F (175°C) and arrange a rack in the middle.
Line a 9×13-inch baking pan with parchment paper, leaving an inch overhang to form a sling.
In a medium bowl, combine the melted butter, yellow cake mix, and 2 eggs. Beat on medium speed until smooth, about 25-30 seconds. The batter will be thick.
Spread the batter evenly into the prepared pan.
In the same bowl, add the softened cream cheese, remaining 2 eggs, powdered sugar, and vanilla extract. Beat on medium-low speed until smooth, about 40-45 seconds. Pour the cream cheese mixture over the cake batter and spread evenly.
Bake for 35-40 minutes, until golden brown around the edges, and the center is slightly jiggly.
Let cool completely on a wire rack for 2-3 hours.
Once cooled, lift the bars out using the parchment paper, place on a cutting board, and slice into 24 pieces.
