Coat an 8 x 4-inch loaf pan with cooking spray; dust with 1 teaspoon flour. Set aside.
Beat butter and sugar at medium speed with a mixer until well-blended (about 4 minutes). Add egg whites and egg, 1 at a time, beating well after each addition. Beat in lemon rind and vanilla.
In a separate bowl, combine 1 ⅔ cups flour and next 4 ingredients (flour through salt), stirring well with a whisk. Add flour mixture to sugar mixture alternately with buttermilk, beginning and ending with flour mixture.
Pour batter into prepared pan; bake in preheated oven for 1 hour or until a toothpick inserted in center comes out clean. Cool in pan 10 minutes on a wire rack; remove from pan.