Preheat oven to 350F with your rack in the lower-middle position.
Whisk together the flour, baking soda, baking powder, pumpkin spice, and salt in a large bowl.
In a medium bowl, whisk together the pumpkin, sugar, butter, eggs, and vanilla. Whisk together.
Add the pumpkin mixture into the dry ingredients and gently mix until just incorporated. The batter will be very thick.
Scoop approximately half of the batter out and back into the other bowl. Add the cocoa powder to one bowl and stir until just incorporated. You should now have an orange batter and a chocolate batter.
Spray a 9x5 loaf pan generously with vegetable oil spray.
Scoop small portions of the orange batter into the pan, covering 1/2 to 2/3 of the bottom.
Switch to the brown batter and scoop small amounts into the gaps and over some of the orange.
Continue going back and forth between the orange and brown batters to make a scattered pattern.
When all the batter is in the pan, firmly whack the pan onto the counter a few times for the batter to settle into any gaps and for air to escape.
Drag a knife through the batter in a swirled, irregular pattern to create more of a marble effect.
Bake at 350F until a toothpick inserted in the middle comes out clean with a few crumbs, approximately 50-60 minutes.
Let the bread cool in the loaf pan for 10 minutes. Dump out the bread (it should come out easily from the spray) and let the bread cool on a wire rack for one hour.
Notes
Learn how to make your own pumpkin spice blend here!Ceramic and porcelain loaf pans can take a little longer than metal pans to bake. You can also bake this in round or rectangular cake pans however the cooking time will be much faster since it is thinner.