Preheat oven to 350

In a large bowl, beat together butter, 1 cup sugar, and egg.

Combine flour, baking powder, baking soda, and salt

Add flour mixture to egg mixture alternately with the buttermilk

In a small bowl, combine the cinnamon and remaining 1/3 cup sugar

Pour a third of batter into greased 8x4x2 inch loaf pan

Sprinkle a third of the remaing cinnamon sugar on top of batter

Repeat layers twice

Bake for 45-50 minutes, or until toothpick inserted near the center comes out clean

Cool in pan for 10 minutes

Remove from pan to a wire rack to cool completely