Preheat the oven to 325°F and set an oven rack in the middle position. Generously grease one 9.25 x 5.25 x 2.75 inch loaf pan with use a nonstick cooking spray with flour in it, such as Baker's Joy.
In a medium bowl, combine the flour, salt, baking soda, baking powder, cinnamon, and pumpkin spice. Whisk until well combined; set aside.
In a large bowl with an electric mixer, beat the butter and sugar on medium speed until blended. Add the eggs one at a time, beating well after each addition. Beat on medium speed for 2-3 minutes until the mixture is very light and fluffy. Add in vanilla and pumpkin and continue to mixture until blended. Please note that the creamy mixture will look curdled or grainy. It is perfectly fine.
Begin adding in the flour mixture a little at a time. Mix on a lower speed working the flour into the batter.
With a wooden spoon or spatula, add in the walnuts and stir until they are throughout the batter.
Add the batter into the greased pans and bake for approximately 75 minutes or until a cake tester inserted into the loaf comes out clean.
Let the pumpkin bread cool in the pan for about 10 minutes, then turn out onto a wire rack or plate to cool completely.
These can be made ahead of time for the holiday. The pumpkin bread can be frozen up to 3 months. I usually will place in a freezer bag.