Preheat the oven to 350 degrees F (175 degrees F). Grease and flour a 9x5 inch loaf pan.
In a medium bowl, combine the dates and butter. Pour boiling water over them, and let stand until cool.
When the dates have cooled, stir the mixture to break up any clumps. Mix in the brown sugar and egg until well blended. Combine the flour, baking soda, baking powder, and salt; stir into the date mixture until just blended. Stir in walnuts. Pour into the prepared pan.
Bake for 50 minutes in the preheated oven, or until a wooden pick inserted into the center comes out clean.