Preheat the oven to 350°F and position the oven rack in the middle. For mini loaf pans: lightly grease the pans and line them with parchment paper, leaving enough to hang over the sides to easily lift the bread out later. If using a brownie pan, line 5 of the wells with 1-inch strips of parchment paper that extend over the sides.
In a medium mixing bowl, combine the egg, granulated sugar, brown sugar, pumpkin, oil, and vanilla extract. Whisk until the mixture is smooth.
Sift or sprinkle the flour, baking powder, baking soda, pumpkin pie spice, and salt over the wet ingredients. Whisk gently until no dry streaks remain. For ease, use a fine mesh strainer to sift the dry ingredients over the wet mixture.
Scoop equal portions of batter into the prepared pans. Sprinkle a generous layer of cinnamon sugar on top of the batter in each section. Using a toothpick or knife, gently swirl the cinnamon sugar on the surface of the batter.
Bake in a brownie pan for 20 to 23 minutes or in two mini loaf pans for 28 to 30 minutes, or until a toothpick inserted in the center comes out mostly clean. Cool the pumpkin bread in the pan on a wire rack for 10 to 15 minutes. Use the parchment paper sling to lift the bread out of the pans and allow it to cool completely on the wire rack.