Preheat the oven to 350 degrees F., and spray a 13x18 inch (half sheet) baking pan. Set aside.
In a large mixing bowl, combine the flour, cinnamon, pumpkin spice, baking powder, salt, and soda. Set aside.
In a medium mixing bowl, mix the sugars together with a whisk. Add the oil and mix until smooth. Mix in the eggs, pumpkin puree, and vanilla and mix well. Add the liquid ingredients to the dry and mix until combined.
Spread the batter evenly into the prepared baking pan. Bake for 18 to 22 minutes, until toothpick comes out clean. Place the pan on a cooling rack and let the cake cool completely before frosting.
Prepare the frosting:
In a large bowl, use a hand mixer or stand mixer to combine the softened butter and cream cheese. Beat for 2 minutes on medium speed. Add the powdered sugar and vanilla and mix until smooth. If you have a lot of air bubbles, mix for 2 minutes on stir to knock them out. If you'd like the frosting thicker, pop the bowl into the freezer for about 20 minutes and then stir again.
Spread the frosting evenly over the cake. Sprinkle chopped pecans on top if desired. Slice and serve. Store covered in fridge.