Start by preheating your oven to 325°F and greasing two loaf pans lightly with butter and flour. In a medium bowl, whisk together the flour, salt, baking soda, baking powder, and spices. Make sure everything is combined well so the spices distribute evenly in the batter.
In a large bowl, beat the softened butter and sugar until blended. Add the eggs one at a time, mixing after each addition so the batter stays smooth. Stir in the canned pumpkin — the mixture may look slightly curdled at this point, which is completely normal.
Add the dry ingredients to the wet mixture and stir gently until everything is just combined. Divide the batter evenly between the prepared loaf pans. Bake for 65–75 minutes, or until a toothpick inserted in the center comes out clean. Let the loaves cool in the pans for 10 minutes, then transfer them to a wire rack to cool completely.