1Preheat oven to 350 degrees F (175 degrees C). Grease and flour a 9x13 inch pan. Squeeze orange and reserve 1/3 cup juice. Grind orange peel and pulp, raisins, and 1/3 cup walnuts together. Set aside.
2In a large bowl, blend flour, 1 cup sugar, baking soda, salt, milk, shortening and eggs. Beat 3 minutes at medium speed. Stir in orange-raisin mixture. Pour into prepared pan.
3Bake in the preheated oven for 35 to 40 minutes, or until a toothpick inserted into the center of the cake comes out clean. Drizzle reserved orange juice over warm cake. Combine 1/3 cup sugar, cinnamon, and 1/4 cup walnuts; sprinkle over cake. Garnish with orange slices.