• Preheat the oven to 350℉. Grease and flour a rimmed 10x15 jelly roll pan with softened butter, shortening, or spray it with cooking spray and then sprinkle on flour to dust the pan. Set aside.
• In a large mixing bowl, whisk together the dry yellow cake mix, brown sugar, pumpkin pie spice, and salt until well combined.
  1 box (15.25 oz) yellow cake mix, 2/3 cup light brown sugar, 1 tablespoon pumpkin pie spice, ¼ teaspoon salt
• In a separate smaller mixing bowl, whisk together the pure pumpkin, buttermilk, oil, eggs and vanilla extract until well combined.

  ^{* You can use the same whisk as before.}
  1 can (15 oz) pure pumpkin, 1/2 cup buttermilk, 1/2 cup vegetable oil, 4 large eggs, 1 teaspoon vanilla extract
• Add the wet ingredients into the dry ingredients and stir it gently with a rubber spatula just until combined and no flour pockets or streaks remain in the batter.
• Pour the cake batter into the prepared pan and bake for 18-23 minutes or until a toothpick inserted into the middle comes out clean.
• Allow the cake to cool completely before frosting it.

Make The Cream Cheese Frosting

• In a mixing bowl using an electric hand mixer, or use the bowl of a stand mixer, to beat the cream cheese and butter until completely smooth and combined. About 1-2 minutes.
• Add in the powdered sugar and vanilla extract. Beat on LOW speed, increasing speed as needed, for 2 minutes until it's smooth and fluffy.
• Frost the cooled cake and cut into squares. Enjoy!

  ^{* If wanted, add some chopped pecans or walnuts as a garnish for the cake on top of the frosting.}