Preheat the oven to 350°F/180°C. Lightly grease a 9x13-inch baking pan with butter or non-stick cooking spray or line with parchment paper. Set aside.
Add the sugar, oil, eggs, and pumpkin puree to a large mixing bowl and beat with an electric mixer for 3 minutes, stopping to scrape down the sides when necessary.
Sift the flour, baking powder, cinnamon, baking soda, nutmeg, and salt into the mixing bowl. Mix gently on low speed or by hand with a wooden spoon until combined.
Pour the mixture into the prepared baking pan and spread evenly to the edges. Bake for 25-30 minutes or until golden, risen and an inserted toothpick comes out clean. Allow to cool in the pan on a wire rack.
For the cream cheese frosting:
Mix the cream and butter: Add the butter to a mixing bowl and beat with an electric mixer until soft. Add the cream cheese and beat again for a few minutes until soft and smooth.
Spread the cream cheese frosting onto the completely cooled pumpkin cake and cut them into bars.