Heat oven to 350°F. Grease and flour 13x9-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 together orange peel and pulp, raisins and 1/3 cup walnuts. Set aside.
Lightly spoon flour into measuring cup; level off. In 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 batter into greased and floured pan.
Bake at 350°F. for 35 to 45 minutes or until toothpick inserted in center comes out clean. Drizzle reserved 1/3 cup orange juice over warm cake in pan.
In 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.