Preheat the oven to 350°F (177°C) and grease a baking pan: a bundt shape or a normal sheet shape would work well.
Whisk the flour, baking powder, baking soda, salt and cinnamon in a large bowl. Set aside. Whisk the oil, eggs, brown sugar, granulated sugar, pumpkin, and vanilla extract together until combined. Pour the wet ingredients into the dry ingredients and use a mixer or whisk until completely combined. Batter will be thick.
Spread batter into the prepared pan. Bake for 30-36 minutes. Baking times vary, so keep an eye on yours. The cake is done when a toothpick inserted in the center comes out clean.
If you find the top or edges of the cake is/are browning too quickly in the oven, loosely cover it with aluminum foil.
Remove the cake from the oven and set the entire pan on a wire rack. Allow to cool completely.
Cover leftover cake tightly and store in the refrigerator for 5 days.