Preheat oven to 180. Grease and line 23 cm (9 inch) round cake tin. Combine dry ingredients in bowl and make a well in the centre. Whisk together milk and egg, pour into well of dry ingredients and whisk to combine.Pour mixture into tin and bake for 20 minutes or until browned lightly. While hot, remove carefully from tin and slice in half, horizontally. Spread the butter on the tops of both the top and bottom layers and allow to melt. Follow this by generously sprinkling the cinnamon/sugar mixture over melted butter. Replace the top of the cake. Slice and serve hot!
You can adjust the quantities of butter, cinnamon and sugar to your liking.