Preheat your oven to 350ºF. Sift flour, baking powder, baking soda, salt, and sugar together into mixing bowl. Pour 1/4 cup of melted butter into 1 cup of measuring cup. Add egg. Fill cup with buttermilk, pour into flour mixture. Beat vigorously for 1 minute or until the batter is smooth. Stir in vanilla. Pour the remaining butter into oven proof skillet or round baking pan. Pour batter into skillet or pan. Arrange the apples on top. sprinkle cinnamon mixture over apples. Bakes for 35 to 40 minutes. Serve hot from pan or cool 5 minutes, invert onto rack, and slide onto serving dish. Serves 8 to 10