In large bowl cream the butter and the sugar. Add the egg and vanilla, beat until blended well. In a small bowl combine the flour,baking powder, and baking soda. Add half the flour mixture, beat. Add the sour cream, beat. Then add the rest of the flour mixture, beat. Grease and flour 1 loaf pan. Blend the cinnamon sugar ingredients in a small bowl.
Spread half the batter in the pan, sprinkle half of the cinnamon sugar on top of the batter. Spread remaining batter in pan then sprinkle rest of cinnamon sugar mix.
Cook for 45-50 minutes or till toothpick comes out clean.