Preheat the oven to 350°F and grease a 9×13-inch baking pan.
In a medium bowl, whisk together the flour, baking powder, baking soda, salt, cinnamon, and pumpkin pie spice. Set aside.
In a large mixing bowl, beat the oil, eggs, brown sugar, granulated sugar, pumpkin, and vanilla with a hand mixer on medium speed for 2 minutes. Scrape down the sides of the bowl, then continue mixing for an additional 30 seconds.
Gradually add the dry ingredients to the wet ingredients in thirds, mixing on low speed until just combined. The batter should be smooth and thick.
Spread the batter evenly in the prepared pan and bake for about 30 minutes. Since baking times can vary, check the cake periodically at the 25 minute mark. It’s done when a toothpick inserted into the center comes out clean. Pro Tip: If the top or edges start to brown too quickly, loosely cover the cake with aluminum foil.
Remove the cake from the oven and place the entire pan on a wire rack. Let it cool completely. After about 45 minutes, you can speed up the cooling process by placing the cake in the refrigerator.