1. PREHEAT the oven to 325°F. Butter and flour two 9-inch round cake pans and set aside.
2. WHISK the flour, baking soda, salt, cinnamon and spices together in a medium bowl. Set aside.
3. MIX the sugars and oil in the bowl of a stand mixer fitted with the paddle attachment. Use medium speed until combined. Add the eggs, one at a time, blending on low speed until each is incorporated. Add the vanilla and the pumpkin purée. Mix until combined and no lumps are present.
4. ADD half of the dry ingredients and mix on low speed until fully incorporated. Add the second half of the dry ingredients, mixing on low speed until incorporated. Use a spatula to fold in the 1/2 cup of nuts; mix until just combined.
5. POUR the batter into the prepared pans and spread it evenly. Bake for 30 to 40 minutes, or until a toothpick inserted in the center comes out clean. Remove from the oven and cool completely.
6. ICE the first cooled cake layer on a serving platter, rounded side down (upside down). Use a knife or angled spatula to spread icing over the top and sides, being generous on top as it will be the filling layer. (A rotating cake stand is a godsend for icing cakes: well worth the modest cost and storage space.) Place the next layer right side up on top of the first and complete the frosting of the top and sides.
7. GARNISH as minimally or lavishly as you like. Minimalist: nothing. Typical: crushed amaretti cookies or ginger snaps. Lavish: chocolate medallions (the Sugar Mommas made chocolate pine cones in a mold) with a chocolate turkey, pumpkin, Christmas tree or reindeer at the center.