Start this recipe by greasing a 23cm/9in square baking tin with butter and line the base and sides with non-stick paper. Preheat the oven to 180`c. To make the caramel topping, put a pan over a high heat. Add the sugar and three tablespoons of water and cook until it the sugar melts and turns an amber colour. Do not stir at any point. Remove from the heat and carefully pour the caramel into the lined baking tin, taking care to cover the base completely. Place the apple wedges in three rows on top of the toffee and sprinkle with the orange zest. Add the cranberries in any gaps between the rows of apple. For the cake, beat the butter substitute and sugar until pale and fluffy. Add the orange zest. Sift together the flour and bicarbonate of soda and add a tablespoon of this to the cake mixture, along with one egg. Mix until combined and repeat the process until all the remaining flour and eggs have been used. Stir in the milk and the vanilla. Pour into cake tin and gently smooth with a spatula. Bake for 40-50 minutes or until a skewer inserted into the centre comes out clean. Using oven gloves, place a cooling rack over the tin and quickly flip over, taking care not to burn yourself on any hot caramel that may leak from the tin. Remove from the tin and set aside to cool down. Tip the cake onto a serving dish whilst still warm, remove the non-stick paper and serve.