Preheat oven to 350 degrees. Grease and flour a 13-by-9-inch pan.
Squeeze orange, reserving 1/3 cup juice for topping; remove seeds. In blender container, food processor bowl with metal blade, or food mill, grind orange peel and pulp, raisins and 1/3 cup walnuts. Set aside.
In a large bowl, combine flour and all remaining cake ingredients at low speed until moistened; beat 3 minutes at medium speed. Stir in orange-raisin mixture. Pour into prepared pan.
Bake for 35 to 45 minutes, or until a toothpick inserted in the center comes out clean.
Drizzle reserved 1/3 cup orange juice over warm cake in pan.
In a small bowl, combine 1/3 cup sugar and cinnamon; mix well. Stir in 1/4 cup walnuts; sprinkle over cake. Cool 1 hour, or until completely cooled.
Time does not include cooling time.