Prepare Cream Cheese Icing; cover and chill.
Coat bottoms of 3 (9-inch) round cakepans with cooking spray (do not coat sides of pans); line bottoms of cakepans with wax paper. Coat wax paper with cooking spray, and dust with flour; set aside.
Beat butter at medium speed of an electric mixer until butter is creamy; gradually add sugar, beating well. Add egg yolks, one at a time, beating well after each addition.
Combine 2 cups flour and baking soda; stir well. Add flour mixture to butter mixture alternately with buttermilk, beginning and ending with flour mixture. Stir in pecans and next 3 ingredients.
Beat egg whites at high speed of mixer until stiff peaks form (do not overbeat). Fold egg whites into batter; pour batter into prepared pans. Bake at 350° for 23 minutes. Cool in pans 5 minutes on wire racks. Loosen cake layers from sides of pans using a narrow metal spatula, and turn out onto wire racks. Peel off wax paper, and cool completely.
Place 1 cake layer on a serving plate, and spread with 2/3 cup Cream Cheese Icing; top with second cake layer. Repeat with 2/3 cup icing and third cake layer. Spread remaining icing over cake. Garnish with lemon rind strips, if desired.