Pockets-of-Lemon Cake

1 package white cake mix
1 1/4 cups water
1/2 cup canola oil
4 large egg whites
1 can lemon pie filling
1 can lemon frosting
8 ounces whipped topping

Heat oven to 350° F. Prepare 9 X 13 pan and set aside. Prepare cake mix as directed on package, using water, oil and egg whites. Spread batter in prepared pan. Drop pie filling by heaping teaspoonfuls evenly onto batter. Bake at 350 degrees for 30-40 minutes or until edges pull away from pan and top is golden brown. Allow cake to cool for 45 minutes or until completely cooled. In medium bowl combine frosting and whipped topping; blend well. Spread over cooled cake. Best if served chilled. Store lightly covered in refrigerator.