Preheat your oven to 350°F (175°C) and grease a 9x13-inch baking dish. Trust me, you'll want easy cleanup later.
In a large bowl, mix the cake mix, melted butter, and 1 egg. Stir until it turns into a thick, sticky dough.
Press this dough evenly into the bottom of your greased pan. Use your fingers or the back of a spoon—whichever keeps you from licking the bowl too early.
In another bowl, beat the cream cheese until smooth. Then mix in the remaining 2 eggs and the vanilla. Blend until creamy and dreamy.
Slowly add the powdered sugar, mixing until everything is smooth. Warning: powdered sugar will try to go everywhere. Consider it part of the magic.
Pour the cream cheese mixture over your cake base and spread it out evenly.
Bake for 35-40 minutes. The edges should be golden and set, but the center stays soft—don’t overbake it!
Cool completely before cutting. Or don’t. I won’t judge.