Step 1

Grease a 10-inch fluted tube pan.

Step 2

Prepare the cake batter according to the package directions, instead replacing 2 teaspoons of the called-for water with 2 teaspoons of the vanilla extract.

Step 3

Add the sour cream to the cake batter and fold to combine.

Step 4

Pour the cake batter in the prepared tube pan and bake according to the package directions.

Step 5

Transfer the tube pan to a wire rack and let the cake cool.

Step 6

Invert the cake onto a serving plate and lightly dust it with the confectioners' sugar.

Step 7

Slice and serve.