Preheat the oven. Preheat the oven to 350 degrees Fahrenheit and grease a large (10-cup) bundt pan with cooking spray or butter and flour the pan tapping out any excess flour. Make sure you grease all the crevices of the bundt pan.
Mix the dry ingredients. Whisk together the flour, baking powder, baking soda, pumpkin spice and salt in a medium mixing bowl.
Mix the wet ingredients and sugar. Whisk together the oil, pumpkin puree, brown sugar, granulated sugar, eggs and vanilla extract in a large mixing bowl. Whisk until just combined.
Combine wet and dry ingredients. Gradually, add the dry ingredients to the wet ingredients and mix until just combined.
Pour the batter. Transfer the batter to the prepared bundt pan smoothing out the top with a spatula or tapping it against the counter a few times.
Bake and cool. Bake for 60 to 70 minutes or until a cake tester or a wooden skewer inserted into the center of the cake comes out clean. Remove from the oven and cool on a wire rack for about 15 minutes, then turn it out onto a cake plate or wire rack to cool completely before frosting.
For the Cream Cheese Frosting
Beat the cream cheese. In the bowl of a stand mixer fitted with the paddle attachment or in a large mixing bowl if using an electric mixer, combine the cream cheese and the butter and beat until light and fluffy.
Add the remaining ingredients. Gradually, add the sifted confectioners’ sugar and mix on medium speed until creamy and smooth. Mix in the milk and vanilla extract. If the frosting appears too thick or too thin, add additional milk or confectioners’ sugar until the desired consistency is reached.
Frost. Spoon over the top of the cool bundt cake. Sprinkle with nuts or chocolate chips if desired (optional).