Preheat oven to 350 degrees and grease a 9 x 5 loaf pan. Set aside.
In your mixer, combine the flour, sugar, baking powder, baking soda, 1½ t. cinnamon, and salt.
In a medium bowl, combine the buttermilk, vegetable oil, eggs, and vanilla.
Slowly add wet ingredients to dry ingredients, and blend well.
Pour into greased loaf pan and smooth the top with a spatula.
In a small bowl, combine the melted butter, brown sugar, and remaining 1 t. cinnamon.
Pour over the mixture in the loaf pan. Using a knife, swirl the cinnamon-butter throughout the loaf.
Bake for 50-55 minutes, or until a toothpick comes out clean.
Cool 5 minutes, then transfer to cooling rack.