Step 1: Preheat your oven to 350°F (175°C). Grease a 9x13-inch baking pan or line it with parchment paper for easy removal.
Step 2: In a medium bowl, combine the dry yellow cake mix, melted butter, and 1 large egg. Mix until evenly combined and a thick, sticky dough forms.
Step 3: Press the dough evenly into the bottom of your prepared baking pan. Use your fingers or the back of a spoon to smooth it out across the entire bottom.
Step 4: In a separate medium mixing bowl, beat the softened cream cheese on medium speed until it is smooth and lump-free.
Step 5: Add the 2 large eggs and 1 teaspoon of vanilla extract to the cream cheese. Beat until fully combined and the mixture is creamy.
Step 6: Gradually add in the 4 cups of powdered sugar, mixing it in batches to avoid a mess. Continue beating until the topping is smooth, thick, and slightly fluffy.
Step 7: Carefully pour the cream cheese mixture evenly over the pressed crust layer in the pan. Gently spread it out to cover the entire surface.
Step 8: Bake for 35 to 40 minutes, or until the top is golden brown around the edges and the center is mostly set with a slight jiggle. Be careful not to overbake, as you want to preserve that gooey texture.
Step 9: Once baked, let the cake cool completely in the pan on a wire rack. This is crucial for the cake to firm up and for clean slicing. For extra neat slices, you can chill it in the refrigerator before cutting.