Preheat oven to 350 degrees F. Spray baking dish or 2 loaf pans. Beat together butter and sugar until fluffy. Beat in vanilla. Add eggs one at a time,blending well after each addition. Combine flour with baking soda and salt. Add to batter alternately with buttermilk,beginning and ending with flour.
Pour batter into prepared baking dish. Bake for about 1 ½ hours or until a pick inserted comes out clean. Allow cake to stand 5 minutes and remove from pan and finish cooling on a rack. Dust with powdered sugar before serving.