Drain the pumpkin: Lay 4 connected sheets of paper towels on a flat surface and fold in half. Spread the pumpkin puree across the folded sheets and set aside for 10 minutes to drain excess moisture.

Preheat the oven to 350 degrees F. Position a rack in the lower third of the oven. Coat a 9×5-inch loaf pan with cooking spray and line with parchment paper, leaving an overhang on the two long sides.

In a large mixing bowl, whisk together the vegetable oil, melted and cooled butter, granulated sugar, and brown sugar until well combined. Add the eggs one at a time, whisking after each addition.

Transfer the drained pumpkin to the bowl. Add the buttermilk and whisk until smooth.

In a separate bowl, whisk together the flour, cinnamon, salt, baking soda, nutmeg, cloves, and vanilla extract (if using). Taste and adjust spices to your preference.

Add the dry ingredients to the wet ingredients and fold together with a rubber spatula until just incorporated, with just a few streaks of flour remaining. Do not overmix.

Pour the pumpkin bread batter into the prepared pan and smooth the top. Bake for 45 to 60 minutes, or until a cake tester or toothpick inserted into the center comes out with just a few moist crumbs. Tent with aluminum foil if the top browns too quickly.

Cool on a wire rack in the pan for 30 minutes. Use the parchment overhang to lift the whole loaf out. Let cool completely before slicing, or eat warm with butter.