In large bowl sift together flour, sugar, baking powder, baking soda and salt. In small bowl, beat together egg, oil, orange juice, orange rind and vanilla. Stir in prepared potatoes. Add orange mixture all at once to dry ingredients and stir to mix well; sift in nuts. Turn into greased 9x5x3 loaf pan. Bake in 325ºF.  oven for 60 min. until cake tester inserted comes out clean. Cool 10 min. Remove from pan and cool completely.