In one bowl combine the flour, 1 cup of the sugar, baking powder, 1 1/2 teaspoons of the cinnamon and the salt.
In a second bowl combine the eggs, buttermilk, vegetable oil and vanilla. Stir the wet ingredients into the dry ingredients until just mixed.
Combine the remaining sugar, cinnamon and melted butter
Pour half of the batter into a 9x5x3 inch loaf pan. Drizzle with the cinnamon, sugar, butter mixture. Swirl with a knife. Pour the rest of the batter into the loaf pan and top with remaining cinnamon/sugar/butter.
Bake at 350 degrees for 55-60 minutes or until toothpick comes out clean. Let cool for 10 minutes in the loaf pan, them remove to wire rack to continue cooling.