Preheat oven to 350F.
Combine dry ingredients (flour, sugar, cinnamon, baking soda, baking powerder, and salt).
Stir in eggs, oil, and pumpkin puree until well combined.
Add 1 cup of chopped pecans, if using (or you can use walnuts, if you prefer), and give it a good stir.
Pour into a greased and floured 13″ by 10″ by 1″ jelly roll pan and use an offset spatula to spread (it will be a thick batter).
Bake for 40 minutes (or until toothpick inserted comes out clean), remove and allow to cool completely.
For the frosting, cream the softened cream cheese, butter, and vanilla until combined.
Add 1/2 of the powdered sugar, mix until you no longer see it, and then add they other half and mix until well combined.
Frost cooled cake and then sprinkle with chopped pecans, if using.