Preheat your oven to 350°F and give a 9″x5″ loaf pan a light coating of cooking spray. In a medium-sized bowl, mix together the flour, baking soda, cinnamon, pumpkin pie spice, baking powder, and salt.
In a larger bowl, whisk the eggs, pumpkin puree, granulated sugar, oil, buttermilk, and vanilla until it’s nice and smooth. Add the dry ingredients and gently fold them in with a rubber spatula until everything is just combined. Take 1 cup of the batter and stir in the Nutella.
Use an ice cream scoop or a measuring cup to place about 1/4 cup of the pumpkin batter in one corner of the prepared pan. Put about 1/4 cup of the Nutella batter right next to it. Keep alternating scoops of batter to cover the bottom of the pan; it will start to look like a checkerboard pattern. Repeat this process to create a second layer.
Take the end of a chopstick or a skewer, and gently drag it back and forth across the batter. Now, rotate the pan 90 degrees and do it again to create a lovely swirling pattern.
Bake the bread until a tester (toothpick or skewer) inserted into the center comes out clean, which should take around 60 to 65 minutes. Let it cool for about 15 minutes. Then, carefully remove the bread from the pan, transfer it to a wire rack, and let it cool completely. Enjoy your homemade, marbled pumpkin bread!