1. Preheat oven to 350°F.
2. Generously spray a standard 9x5 loaf pan with nonstick cooking oil. Dust about 1-2 teaspoons of flour in the inside of the loaf pan, covering the inner sides and bottom. (Alternatively, you can use butter to grease the loaf pan).
3. Crack the eggs in a small bowl, then lightly beat the eggs with a whisk. Stir in the vanilla extract to the bowl of lightly beaten eggs, then set aside.
4. In a medium mixing bowl, add the flour, baking powder, baking soda, and salt. Whisk together to incorporate and set aside.
5. In a separate large mixing bowl, add the pumpkin purée, melted butter, brown sugar, cinnamon, ginger, clove, and allspice. Use a whisk or silicone spatula to evenly blend, for about 20 seconds.
6. Add half of the flour mixture to the bowl of pumpkin mixture, making sure to stir with a silicone spatula or wooden spoon to blend. Then, add the remaining flour and continue to stir until incorporated. Do not over blend. Pour the batter in the prepared loaf pan. Smooth the top of the batter evenly with a spatula.
7. Place the loaf in the oven and bake for 45 to 55 minutes, or until a toothpick inserted into the center comes out clean. After approximately 35 minutes, loosely cover the loaf with aluminum foil, then continue baking for the remaining time until it is fully cooked.
8. Remove the loaf from the oven and set aside to cool for 45 minutes to 1hour. Turn out the loaf onto a wire cooling rack.

Icing

1. In a medium bowl, add the Confectioner's sugar, melted butter, and pumpkin purée. Stir vigorously with a spoon, then add in the vanilla extract, and maple syrup. Blend until smooth and slightly thick. Consistency should coat the back of a spoon. Drizzle and spread the icing over the loaf. Sprinkle chopped walnuts over the loaf cake. Slice and enjoy!