Preheat your oven to 350°F (175°C) and prepare your loaf pan by greasing it or lining it with parchment paper.

Melt unsalted butter over medium heat in a light-colored saucepan, stirring regularly until it turns golden brown, about 5-7 minutes.

In a large bowl, combine cooled brown butter, pumpkin puree, sugar, and eggs. Add cinnamon, nutmeg, and allspice, and whisk until smooth.

In another bowl, whisk together flour, baking soda, baking powder, and salt.

Gradually combine dry ingredients with the wet mixture using a spatula, folding gently until just combined.

Pour the batter into the loaf pan and smooth the top. Bake for 45 minutes or until a toothpick comes out clean.

Let the bread cool in the pan for 15 minutes, then transfer to a wire rack to cool completely.

Whisk together maple syrup and powdered sugar in a small bowl until smooth to prepare the glaze.

Once cooled, drizzle the glaze over the bread, allowing it to run down the sides.