Prepare the oven and baking pans. Preheat the oven to 350°F (175°C) with the oven rack positioned in the center.

For mini loaf pans, apply a light coating of grease and line the pans with parchment paper, allowing enough parchment to extend beyond the edges to serve as lifting handles.

When using a brownie pan, place approximately 1-inch-wide parchment strips into five cavities, leaving the ends extending over the sides. This will help prevent sticking and simplify removal after baking.

Combine the wet ingredients. Place the egg, granulated sugar, brown sugar, pumpkin purée, neutral oil, and vanilla extract in a medium mixing bowl. Whisk thoroughly until the mixture is uniform, smooth, and free of visible lumps.

Add the dry ingredients. Sift the all-purpose flour, baking powder, baking soda, pumpkin pie spice, and salt directly over the pumpkin mixture. A fine-mesh sieve may be used, or the ingredients can be distributed evenly across the surface.

Whisk gently just until the flour disappears and no dry patches remain. Avoid excessive mixing, which can produce a firmer, less tender texture.

Portion the batter and create the cinnamon swirl. Divide the pumpkin batter evenly among the prepared pan cavities or mini loaf pans.

Sprinkle 2 to 3 tablespoons of cinnamon sugar generously over the batter. Using a toothpick or the tip of a knife, lightly draw the cinnamon mixture through the upper surface of the batter to form a marbled swirl.

Bake the pumpkin bread. Transfer the pan to the preheated oven. For a brownie pan, bake for 20–23 minutes. For mini loaf pans, bake for approximately 28–30 minutes.

Check for doneness by inserting a toothpick into the center of the bread. It should emerge mostly clean when the bread is fully baked.

Cool before serving. Set the pan on a wire cooling rack and allow the pumpkin bread to rest for 10–15 minutes.

Using the overhanging parchment as handles, carefully lift the bread from the pan. Transfer it directly to the wire rack and allow it to cool completely before slicing for the neatest portions and fullest flavor.