1 (18 ounce) package white cake mix
1 (3.1 ounce) package instant frosting mix
3/8 cup hot water
1/2 cup white sugar
1/2 cup butter
Preheat oven to 350 degrees F (175 degrees C). Lightly grease a medium-size 10 inch tube or Bundt pan.
In a large bowl, stir together the cake mix, instant frosting mix, hot water, and sugar. Beat for 2 minutes at high speed of an electric mixer. Gently stir in the butter. Pour batter into prepared pan.
Bake in the preheated oven for 40 to 45 minutes, or until a toothpick inserted into the center comes out clean. Immediately invert onto a wire rack and carefully remove from oven. Cool for 1 hour, then transfer to a wire rack to cool completely. Frost with the remaining frosting.