Place dates in bowl, add baking soda, pour boiling water to cover dates. Mix well until smooth with a spoon and let stand until cool. Beat egg until light, add sugar gradually add salt and vanilla. Combine with dates mixture. Stir flour and baking powder together. Add to dates mixture. Add cool melted butter and walnuts. Put in loaf pan. Bake 350 F for 50 to 60 minutes.