Mix together flour, salt, sugar and butter until crumbly. Measure and set aside 3/4 cup of the mixture. To the remainder add the baking powder, soda, cinnamon, egg, and buttermilk. Beat until smooth. Spread batter in a greased 8" square pan. Bake in preheated 350 deg f oven for 50 to 60 minutes or until a wooden pick comes out clean. Cool 10 minutes. Cut into 9 pieces and serve warm.