White Cake with Pistachio Frosting

I think this is the birthday cake my mom made me this year. It was really good but kind of messy. I think I may make a version of this with the bog cake recipe using white cake mix, applesauce, and mandarin oranges. Then I'll frost it with this pistachio frosting. Yum Yum!


INGREDIENTS
CAKE

18 1/4 ounces white cake mix
3 egg whites
2 1/2 cups diet 7-Up

FROSTING
1(1ounce)package sugar-free pistachio instant pudding
8 ounces fat-free cool whip(small)
1 cup diet 7-Up

DIRECTIONS
Mix all ingredients together. Spray 13 x 9 pan. Bake at 350 degrees for 30 - 35 minutes. Test cake top by lightly touching the center which should feel slightly firm and will slightly spring back to the touch. (Cool cake completely before frosting.). Mix together frosting ingredients and spread over cake. Refrigerate until ready to eat and hold in the fridge for up to two weeks.