Preheat oven to 350 F degrees
Cream together sugars and butter in a large mixer bowl
Measure the buttermilk into a liquid measuring cup and add the baking soda then slowly add to sugar and butter mixture
In a medium bowl mix together (by hand) the pumpkin and egg - then add it to the sugar mixture.
Place flour, baking powder, spices, and chopped nuts in a medium bowl and mix by hand
Alternate adding the flour mixture and the buttermilk mixture beginning with the flour.
Scraping down the sides of the mixing bowl as you add ingredients
Add cake batter to a greased 9" x 5" loaf pan
Bake for 65 to 75 minutes