Butter a 10-cup loaf pan. Dust with fine, dry bread crumbs, and tap out excess crumbs. Sift together flour, baking powder, baking soda, and salt. Set aside. In a large mixer bowl, cream the butter. Beat in vanilla. Add sugar and beat only until well mixed. Add the eggs one at a time, beating only until incorporated. Beat for about 1 minute more. On low speed, add the dry ingredients alternately with the buttermilk, beating until incorporated after each addition. Stir in grated rind. Turn into prepared pan and shake the pan a bit to level. Bake at 325, on a rack 1/3 up from bottom of oven, for 1 hour and 30 to 35 minutes, or until cake tests done. The top will be richly brown. Let cool in the pan for 10 to 15 minutes. Invert onto a rack, then again onto first rack, so that cake cools upright without the pan. Wrap and refrigerate (or freeze for about an hour) before serving.