Preheat oven to 350°F, position the oven rack to the middle position, and spray a rimmed sheet pan (11x15 inches) with nonstick baking spray. Set aside.
In a large mixing bowl, whisk the flour, baking powder, baking soda, salt, cinnamon, and pie spice together. Set aside.
2 cups all-purpose flour, 2 teaspoons baking powder, 1 teaspoon baking soda, ½ teaspoon kosher salt, 1½ teaspoons ground cinnamon, 1½ teaspoons pumpkin pie spice
In the bowl of a stand mixer fitted with the paddle attachment, beat the sugar and oil together on medium speed until well incorporated, about 1 minute.
2 cups granulated sugar, 1 cup canola oil
Add eggs, one at a time, mixing well after each addition.
4 large eggs
Add pumpkin puree and mix for 1 minute.
15 ounces pumpkin puree
Set the mixer to the lowest speed and add the flour (1 cup at a time) until no flour is visible. Turn mixer to medium speed and beat 1-2 minutes, or until smooth and flour is completely incorporated.
Pour the pumpkin batter into the prepared pan and rap the pan on the counter to release any batter bubbles.
Bake 25-33 minutes, or until a toothpick inserted in the middle comes out clean.
Transfer the cake to a wire cooling rack to cool completely.
While the cake cools, make the frosting. Place the cream cheese in the bowl of a stand mixer fitted with the paddle attachment and beat on medium-high speed for 1 minute.
8 ounces cream cheese
Add the butter and mix until incorporated, about 1 minute.
5 tablespoons unsalted butter
Add the sour cream, vanilla extract, and salt. Reduce the speed to medium and beat for an additional 1 minute.
2 tablespoons sour cream, ½ teaspoon pure vanilla extract, ⅛ teaspoon kosher salt
Add the powdered sugar and beat until fluffy and smooth, about 2-3 minutes.
1½ cups powdered sugar
Frost the cooled cake with the frosting, top with pecans (if desired), cut into squares, and serve.
1 cup roasted chopped pecans