Preheat your oven to 350°F (175°C). Grease a 9x13 inch baking pan.
In a mixing bowl, whisk together the pumpkin puree, brown sugar, vegetable oil, eggs, and vanilla extract until smooth.
In another bowl, combine the flour, baking powder, baking soda, salt, cinnamon, nutmeg, and cloves.
Gradually add the dry ingredients to the wet ingredients, mixing until just combined.
Pour the batter into the prepared baking pan and spread it evenly.
Bake for 25-30 minutes, or until a toothpick inserted into the center comes out clean.
Allow the bars to cool in the pan before cutting into squares and serving.