Lemon-Cream Cheese Muffins

1 pkg. white cake mix
1 pkg. (4-serving size) Jell-O lemon flavor instant pudding
1 cup water
4 egg whites
2 Tbsp oil
1 pkg. (16 oz.) powdered sugar
1 pkg. (8 oz.) cream cheese, softened
1 stick butter, softened
2 Tbsp. lemon juice

Preheat oven to 350. Beat cake mix, dry pudding mix, water, egg whites, and oil in a large bowl. Spoon battter evenly into 24 paper lined muffin cups. Bake 20 min. Test with a toothpick, if it comes out clean, remove from oven and cool completely. Meanwhile, beat sugar, cream cheese, butter, and juice until well blended. Put frosting in a ziplock baggie, and cut off one of the ends about 1/4 in. Swirl the frosting on the cupcakes.