Preheat oven to 350 degrees.
Wash orange, and coarsely chop in a meat grinder or blender. Add to orange juice.
Combine flour, sugar, baking powder, baking soda, and salt. Stir in the chopped cooked prunes and the chopped walnuts.
Beat together orange mixture, egg, butter, and vanilla. Add to dry ingredients and beat for about half a minute.
Turn into greased 9-inch by 5-inch by 3-inch loaf pan, or 3 mini loaves.
Bake at 350 degrees for 60 to 65 minutes for loaf pan or about 40 minutes for mini loaf pans.