Peel, core and chop the apples in smaller chunks.
Melt the cold butter in a sauce pan, add the chopped apples together with the brown sugar, cinnamon and half a cup of water.
Leave to cook for 3-4 minutes until the apples are slightly tender, and the liquid is evaporated.
Butter a cake tin (non-detachable walls) well with butter, and arrange the apples in a single layer.
In a food processor, add the flour, granulated sugar, soften butter, baking power, bicarb of soda, eggs, vanilla extract and milk.
Blitz well until you get a smooth paste.
Pour the batter over the apples, and bake in the preheated oven at 180 degrees Celsius (350 Fahrenheit) for 30 minutes or until the top is golden and a toothpick inserted in the middle comes out clean.
Run a sharp knife around the edges of the cake, place a large plate on top, and turn the cake upside down in a swift move.
Leave to cool before slicing.