Cream margarine. gradually add sugar. Beat until light and fluffy. Add eggs, one at a time, beating well after each addition. Combine dry ingredients. Add alternately with buttermilk, beginning and ending with flour. Stir in nuts and vanilla. Pour into greased and floured 25 cm tube pan or Bundt pan. If preferred, use cooking spray to prepare pan. Bake at 180ºC or 1 hour and 15 minutes or until cake tests done. Cool in pan 10 to 15 minutes. Remove from pan and cool completely.