Make the Pumpkin bread
Pre-heat the oven to 350°F and grease an 8½" loaf pan if not adding nuts or a 9" loaf pan if using nuts.
In medium-sized mixing bowl, whisk the flour, salt, cinnamon, baking powder, baking soda and xanthan gum together,
In a large mixing bowl, whisk the oil, sugar, eggs, pumpkin, and vanilla.
Add the dry ingredients to the wet and stir with a rubber spatula until combined. Then stir with a whisk until smooth.
Stir in the nuts if using.
Pour into the loaf pan and bake for 45 minutes. Then cover with a foil tent and bake another 20-25 minutes or until the top is set and a toothpick inserted in the center comes out dry.
Make the Rum Icing
Add the sifted powdered sugar to a small bowl.
Stir in the rum and 1 tsp water. Stir until smooth. Stir in the sour cream. If it is too thick, add more water, 1 tsp at a time.
Drizzle over the cooled loaf just before serving.