Preheat your oven to 350°F (175°C). Grease and flour the loaf pan.
In a medium bowl, sift together the flour, baking powder, baking soda, salt, and spices (cinnamon, nutmeg, ginger). Set aside.
In a large bowl, cream together the softened butter and sugar until light and fluffy, using an electric mixer if desired.
Add the eggs one at a time, mixing after each addition until fully incorporated.
Blend in the pumpkin puree, buttermilk, and vanilla extract until the mixture is smooth.
Gradually add the dry ingredients to the wet ingredients, mixing gently until just combined. Do not overmix.
Pour the batter evenly into the prepared loaf pan.
Bake in the preheated oven for 60 minutes, or until a toothpick inserted into the center comes out clean.
Once baked, remove from the oven and let the cake cool in the pan for about 10 minutes. Then transfer it to a cooling rack to cool completely.