Preparation
Preheat oven to 350. Grease & flour loaf pan. Cream butter with 1/2 cup sugar & brown sugar until light & fluffy. Add egg & beat well. Sift flour with baking soda, salt, tsp cinnamon, & baking powder. Mix banana with buttermilk in small bowl.
Add flour alternately with the banana & buttermilk mixture to the butter mixture, stirring after each addition until smooth. Pour batter into prepared pan. Combine 1/2 tsp cinnamon with 2 Tbsp. sugar, mix well & sprinkle over batter.
Bake for 350 for 45 minutes to 1 hour. Remove from oven & then from pan & cool on a wire rack. Store in plastic bag.