Preheat your oven to 350°F (175°C). Grease two 9x5-inch loaf pans.
Cream butter, 2 cups sugar, and eggs. Add buttermilk, flour, and baking soda.
Put ½ of batter into greased loaf pans (¼ in each).
Mix together ingredients for cinnamon sugar mixture in a bowl. Sprinkle ¾ of cinnamon mix on batter in pans.
Add remaining batter, sprinkle with rest of cinnamon mix.
Swirl with a knife.
Bake for 45-50 min or until a toothpick comes out clean. Cool in pan before removing.
