Preheat the oven to 325°F, and line a 9x5-inch loaf pan with parchment paper.
Whisk the flour, baking soda, baking powder, salt, and spices together until well combined.
Whisk the pumpkin puree, granulated sugar, brown sugar, oil, eggs, and vanilla extract until thoroughly mixed.
Pour the wet ingredients into the dry ingredients and stir until combined. Make sure there are no streaks of flour, but be careful not to overmix.
Pour the batter into the prepared loaf pan and sprinkle with the chopped pepitas.
Bake at 325°F for 1 hour and 10 minutes to 1 hour and 20 minutes. The loaf is done when it's well risen and cracked, browned, and has an internal temperature of 200°F on a digital thermometer.
Let the loaf cool for 10 minutes in the pan, then use a knife to loosen the edge and use the paper to lift the loaf out of the pan. Discard the paper and let the bread cool completely on a wire rack, at least 1 hour.
Once the loaf has cooled, slice in thick pieces and serve with coffee or tea.