Cake: Preheat oven to 350F/180C. Coat two, 8-inch round cake pans with cooking spray, dust lightly with flour and set aside. Combine flour, baking powder, baking soda, and salt. Set aside. Mix granulated sugar and butter in a large bowl; beat with a mixer at medium speed until well blended. Add eggs, one at a time, beating well after each one. Add flour mixture and non-fat buttermilk alternately to sugar mixture. Beat in lemon peel, vanilla and lemon juice. Pour batter into prepared pans. Bake for 30–35 minutes or until a wooden toothpick inserted comes out clean.
Icing: Combine all ingredients in a large bowl. Place one cake layer on a plate; spread half of the icing on top of cake. Add the second cake layer and top with remaining frosting.