Preheat your oven to 350°F (175°C). Grease a 9×5 inch loaf pan with butter or non-stick cooking spray. For easy removal, you can also line the pan with parchment paper, leaving a slight overhang on the sides.
In a medium mixing bowl, whisk together the all-purpose flour, baking soda, baking powder, salt, and pumpkin pie spice. Ensure there are no large lumps and the spices are evenly distributed.
In a large bowl, combine the pumpkin puree, 0.5 cup granulated sugar, brown sugar, melted butter, egg, and vanilla extract. Whisk until the mixture is smooth and the sugars have mostly dissolved.
Gradually add the dry ingredients into the wet ingredients. Use a spatula to fold the mixture together until just combined. Be careful not to overmix, as this can make the bread tough.
In a small bowl, mix the remaining 0.25 cup of sugar and 1 tablespoon of cinnamon together until well blended.
Pour about half of the pumpkin batter into the prepared loaf pan. Sprinkle about two-thirds of the cinnamon-sugar mixture evenly over the batter. Top with the remaining batter. Sprinkle the rest of the cinnamon sugar on top. Use a butter knife to gently swirl the layers together in a zig-zag motion.
Place the pan in the center of the oven and bake for 50 to 60 minutes. The bread is done when a toothpick inserted into the center comes out clean or with just a few moist crumbs attached.
Let the bread cool in the pan for about 10 minutes. Then, transfer it to a wire rack to cool completely before slicing. This helps the structure set so you get clean slices.