In a bowl, combine flour, 1 cup sugar, baking powder, 1 ? teaspoons cinnamon and salt. In another bowl, combine the eggs, buttermilk, oil and vanilla, stir into dry ingredients just until smooth. Pour half of the batter into a greased 9X5X3 loaf pan. In a small bowl combine the remaining sugar and cinnamon; stir in butter. Drizzle half over batter; cut through with a knife to swirl. Top with remaining batter. Drizzle with remaining cinnamon sugar mixture; swirl with a knife. Bake at 350? for 55-60 minutes or until a toothpick inserted near the center comes out clean. Cool for 10 minutes before removing from pan to a wire rack.