Grease a 13x9x2 inch baking pan; set aside. Use a vegetable peeler to remove the zest from the orange. Juice the orange, reserving 1/3 cup; set aside. In a food processor place the zest, raisins, and walnut pieces. Cover and process until finely ground; set aside.
In a large bowl with an electric mixer on med to high speed beat together the shortening and 1 cup sugar until combined. Add eggs and beat until combined. In a small bowl stir together the buttermilk and baking soda until soda is dissolved. Add to flour mixture with vanilla and beat until combined. Stir in raisin mixture. Spoon batter into prepared pan.
Bake in a 350 degree oven for 30 minutes.
Meanwhile, in a small bowl stir together 1 cup sugar and reverved orange juice until combined. Remove cake from oven. Pour sugar mixture over cake. Return to oven; bake for 8 to 10 minutes more or until topping is bubbly. Cool on wire rack.