Mix together flour, salt, sugar and butter until crumbly. Measure and set aside 0.75 cup of the mixture. To the remainder add the baking powder, soda, cinnamon, egg, and buttermilk. Beat until smooth. Spread batter in a greased 20 cm 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.