In a large bowl, combine flour, 1 C. sugar, baking powder, 1 1/2 tsp. cinnamon, and salt.
In a small bowl, combine eggs, buttermilk, oil, and vanilla. Stir into dry ingredients, just until smooth.
Pour 1/2 the batter into a greased 9x5x3 loaf pan.
In a small bowl, combine the remaining cinnamon and sugar. Stir in melted butter.
Drizzle 1/2 of this mixture over batter in loaf pan. Cut through with a knife to swirl.
Repeat with the remaining batter and cinnamon mixture.
Bake at 350 degrees for 55-60 minutes, or until it tests done.
Cool 10 minutes in pan, then remove to rack to finish cooling.
Hint: Make ahead and freeze smaller loaves to give as gifts, or to slice and serve as a "side dish"
to serve with bacon and eggs for a special breakfast.