Preheat oven to 350?F. In a blender or food processor, grind 1 whole seedless orange (skin and all) with raisins and walnuts until finely chopped.
In a bowl, cream butter and sugar; beat in eggs. In another bowl, mix flour, baking powder, baking soda, salt. Add dry ingredients to creamed mixture alternately with milk. Stir in the orange-raisin-nut mixture. Pour into a greased 13?9 pan. Bake ~30?35 min until toothpick comes out clean. While warm, glaze with a mixture of fresh orange juice and sugar. Cool to serve..