Preheat oven to 350°F. Line 8-inch square pan with foil, extending foil over 2 sides for easy removal later; spray foil with cooking spray. In mixing bowl, cream together cookie mix and butter. Add 1 whole egg, vanilla and lemon zest. Beat until completely blended. Fold in beaten egg whites. Reserve 1/2 cup of the cookie dough for top. Spread remaining dough in prepared pan and bake15 minutes.
While bottom portion is baking, combine jam with1 tsp. of lemon juice. Spread jam mixture on cookie base after baking first time. Crumble remaining cookie dough onto top of bar base. Bake 20 minutes or until cookie dough top is light brown.
In small bowl, mix powdered sugar and 1tsp. of remaining lemon juice until smooth. If necessary add more lemon juice to make a drizzling consistency. Let bars stand for 15 minutes. Remove from pan using foil handles. Cut into bars.