Pre heat oven to 350 degrees. Grease the bottom and sides of an 8 inch loaf pan.
1. In a large bowl beat butter, 1 cup sugar and egg until well incorporated.
2. In a medium bowl combine the flour, baking powder, baking soda and salt, stir to combine.
3. Add the flour to the egg mixture alternately with the buttermilk. Start with 1/3 of the flour, half of the buttermilk, 1/3 of flour, the remaining buttermilk and then adding the last 1/3 of flour. Mixing with each addition just until incorporated.
4. In a small bow, combine the cinnamon with 1/3 cup of sugar.
5. Using the prepared 8 inch greased loaf pan, place 1/3 of the batter into the bottom of the loaf pan. Sprinkle 1/3 of the cinnamon/sugar mixture over the batter. Repeat the layers 2 more times , ending with the last 1/3 of cinnamon sugar as the topping.
6. Bake at 350 degrees for 45 minutes or until a tooth pick inserted in the center comes out clean. Remove from the oven, cool 15 minutes before removing the loaf from the pan to a cooling rack to cool completely.