Preheat your oven to 200 degrees Celsius. Sift the flour, baking powder and salt together in a large mixing bowl. Add a half a cup of sugar. Slice off 50g of the butter and set it aside. Then (and I know this is strange for a cake method, but it works!) use a box grater to grate the remaining 200g of butter into the flour mix. (Top tip: If the butter becomes too warm while you’re working with it and won’t grate properly, pop it in the freezer for a few minutes.) Use a fork to stir the grated butter into the flour mix. Beat together the milk, egg and vanilla essence. Add it to the flour and use a fork to mix. The mixture will be quite lumpy initially, but it does all come together in the end.
Spray a 20cm spring-form cake tin with non-stick cooking spray. Spoon the buttercake batter into the tin – it is quite a thick batter. Peel, halve and core the apples and cut into thin slices. Cover the batter with the sliced apple. Melt the remaining 50g of butter that you set aside and stir in a third of a cup of sugar and the cinnamon. Spoon and spread this mix over the apples. Pop the cake in the oven and bake for 30-40 minutes. To check if it’s done, stab it with a thin knife or kebab stick – if it comes out clean, the cake is ready. If dough clings to the knife, it needs a few minutes more. Serve this buttercake slightly warm with whipped cream or warm custard.