Preheat the oven to 350 degrees.
Grease and flour a 13 X 9 inch baking pan.
In a medium saucepan, bring the raisins and water to a boil; simmer for 1 minute.
Remove from heat and cool slightly.
Stir in sugar and oil.
Add the egg.
Combine the flour, cocoa, baking soda, salt, and cinnamon, then stir into the raisin mixture, blending well.
Stir in the nuts.
Pour the batter into prepared pan.
Bake 25 - 30 minutes or until toothpick inserted in center comes out clean.
Place on a wire rack to cool in the pan.
When cool, sprinkle with powdered sugar.