Heat the oven to 350°F.

Prepare the cake mix as directed.

Pour half the batter into a greased 9-inch springform pan.

Beat cream cheese, sugar, eggs, vanilla, and sour cream until smooth.

Spread the cheesecake mixture over the batter.

Add the remaining batter on top.

Bake for 55 to 65 minutes, until the center barely jiggles.

Cool completely, then refrigerate for at least 4 hours.

Spread whipped topping over the chilled cake before slicing.