Combine orange juice, orange peel, and dates or raisins. Let this soak while preparing the rest of the cake batter. Stir together flour, sugar, baking powder, and salt. Make a well in the center. Combine milk, oil, and egg; add all at once to the dry ingredients. Stir just until mixed. Add orange juice mixture. Stir just until blended. Spread evenly in a greased 11x7x1 1/2 inch baking pan. Combine walnuts, brown sugar, butter and cinnamon. Sprinkle over batter. Bake at 375 for about 30 minutes.