Preheat oven to 350 degrees. Spray a 6 x 10 inch, 8 x 8 inch, or 9 inch round pan with cooking spray.
Mix dry cake ingredients together in a large bowl.
Beat together eggs, water, oil, and pumpkin in a small bowl.
Add egg mixture to dry ingredients and beat with an electric mixer until thoroughly combine.
stir nuts and raisins into batter.
Pour batter into prepared pan and bake 50-60 minutes, until edges are just browned and center begins to crack.
Cool cake before frosting.
For frosting: mix all frosting ingredients together with an electric mixer. Garnish with chopped nuts and nutmeg, if desired.