Preheat your oven to 350°F and position the oven rack in the middle. Prepare a rimmed sheet pan (11×15 inches) by spraying it with nonstick baking spray. This ensures easy removal of the bars once they’re baked.
In a large mixing bowl, combine the flour, baking powder, baking soda, kosher salt, cinnamon, and pumpkin pie spice. Whisk them together until they are well mixed. Set this mixture aside to use later.
In the bowl of a stand mixer fitted with the paddle attachment, combine the granulated sugar and canola oil. Beat on medium speed for about one minute until they are well incorporated and slightly creamy.
Add the eggs, one at a time, mixing well after each addition. This allows each egg to blend thoroughly into the mixture, creating a rich batter.
Next, add the pumpkin puree and mix for about one minute until well combined. The batter should be thick and orange at this point.
Reduce the mixer speed to low and gradually add the flour mixture, about one cup at a time, until no flour is visible. Once all the flour is added, increase the speed to medium and mix for 1 to 2 minutes until the batter is smooth and fully combined.
Pour the pumpkin batter into the prepared pan. Gently rap the pan on the counter to release any air bubbles, ensuring a uniform texture.
Bake in the preheated oven for 25 to 33 minutes, or until a toothpick inserted in the center comes out clean. Keep an eye on them as baking times may vary slightly.
Once baked, transfer the cake to a wire cooling rack. Allow it to cool completely before frosting.
While the cake cools, let’s make the frosting. In the bowl of your stand mixer, add the cream cheese and beat on medium-high speed for one minute until it’s smooth and creamy.
Add the unsalted butter to the cream cheese and mix until incorporated, about one minute.
Next, add the sour cream, vanilla extract, and kosher salt. Reduce the speed to medium and mix for an additional minute.
Finally, add the powdered sugar and beat until fluffy and smooth, approximately 2 to 3 minutes.
Once the cake is cool, frost it generously with the cream cheese frosting. If desired, top with roasted chopped pecans for added flavor and texture. Cut into squares and serve.
