Squeeze the juice from the orange setting aside 1/3 cup juice.
Remove orange seeds and grind the orange along with the orange peel, the raisins and walnuts. I use a blender to do the grinding. You can use a food processor, an old-fashioned table grinder or whatever you have available. I also cut the orange in pieces with the peeling still on for grinding in the blender.
In a bowl whisk together the flour, sugar, baking soda and salt.
Add the shortening, milk and eggs and mix with a mixer.
Add in the ground up orange, raisins and walnuts and continue to mix until all ingredients are wet.
Spray a 9 x 13 baking pan with cooking spray. Pour in the cake mixture and bake in a preheated 350 degree oven for 30 to 35 minutes or until the center of the cake tests done.
Add topping below.
Topping Instructions:
Pour the reserved 1/3 cup orange juice over the hot cake. Stir together the cinnamon, sugar and chopped walnuts and sprinkle over cake after adding the orange juice.
Notes
I have found that a regular orange with seeds works better than one of the seedless navel oranges when it comes to grinding the peeling.