Preheat oven to 350. In a large bowl, cream butter and sugar until light and fluffy, 5-7 minutes.
Add eggs one at a time, beating well after each one.
Beat in pumpkin
In another bowl, whisk flour, 1/2 tsp cinnamon, baking powder, salt and baking soda; add to the creamed mixture alternately with buttermilk, beating well after each addition.
Remove 1/2 cup of batter to a small bowl; stir in 1 tsp cinnamon and molasses until blended.
Pour half the remaining batter into a greased 8x4 loaf pan. Dot with 1/2 of the cinnamon batter mixture. Repeat layers. Cut through batter with a knife to swirl.
Bake until a toothpick inserted inserted in the center comes out clean, about 45-50 minutes.
Cool in pan for 20 minutes before removing to a wire rack.