Preheat your oven to 350°F (175°C) and grease two 9x5 inch loaf pans.

In a large mixing bowl, cream together butter, 2 cups sugar, and eggs.

Mix in buttermilk, flour, baking soda, and 1 teaspoon of cinnamon. Divide half of the batter between the two loaf pans.

In a small bowl, combine brown sugar, remaining cinnamon, and walnuts. Sprinkle half of this mixture over the batter in the pans.

Pour the remaining batter over the top and then sprinkle with the remaining brown sugar mixture. Use a knife to swirl the batter.

Bake for 45-50 minutes, or until a toothpick inserted into the center of the loaf comes out clean.