Preheat oven to 350°. Grease and lightly flour 9x5-inch loaf pan or line muffin tin with paper liners.
Cream 1½ cups brown sugar and ½ cup oil. Add 2 large eggs and ½ pound pumpkin puree. Combine well.
In a separate bowl, sift together 1½ cups all-purpose flour, 1 teaspoon baking soda, ¼ teaspoon baking powder, 1 teaspoon cinnamon, 1 teaspoon ground ginger, ½ teaspoon nutmeg, ½ teaspoon allspice, and ½ teaspoon salt.
Stir the dry ingredients into the wet pumpkin mixture in 3 additions, alternating with ⅓ cup buttermilk, beginning and ending with dry ingredients.
Pour into loaf pan or divide into muffin tin. Sprinkle pumpkin seeds over the top, concentrating toward the center. Lightly tap into batter to help stick.
Bake loaf pan for approximately 50 minutes or muffins for 25 minutes, checking with toothpick about 10 minutes before.