In a small bowl, combine the dates and water; let stand for 15 minutes (do not drain). In a bowl, cream butter and brown sugar; add egg and mix well. Combine flour, baking soda and salt; add to the creamed mixture alternately with dates and liquid. Stir in walnuts.
Pour into a greased 8x4-in. loaf pan. Bake at 350° for 60-65 minutes or until a toothpick inserted in the center comes out clean. Cool on a wire rack.