Preheat oven to 350F and grease a loaf pan, set aside.
In a large bowl, whisk all the dry ingredients together and add the buttermilk, egg, and oil.
Mix until combined.
Pour half the batter into loaf pan and sprinkle enough cinnamon sugar to coat the top. Pour the rest of the batter on top, sprinkle more sugar to coat top.
Using a knife, swirl the batter with the cinnamon sugar, like making figure 8's.
Bake for 45-55 minutes, until toothpick comes out clean.