In the bowl of a stand mixer or a mixing bowl, cream together the butter and 1 ½ cup sugar then add in the eggs, pumpkin puree, sour cream, and vanilla extract. Mix until combined.
In a medium bowl, whisk together the flour, pumpkin pie spice, salt, and baking soda.
Add the wet ingredients to the dry ingredients and stir just until combined. Do not over mix.
Prepare a 9x5 loaf pan by spraying non-stick cooking spray, then sprinkling the pan with the remaining ½ cup of sugar. Pour batter into the pan.
Bake the bread at 350 degrees for 65-75 minutes or until a toothpick or cake tester inserted into the center of the bread comes out clean.
Allow the pumpkin bread to cool in the pan for 15 minutes before removing from the pan and transferring to a wire rack. Once cool, cut into thick slices.