Spiced apple sauce cake

Method

1. Peel, core and slice the apples and put in a non-stick saucepan. Add the lemon juice and 2 tablespoons water. Cover and cook over a low heat until broken down into a purée. Uncover, increase the heat slightly and cook for 5 minutes or so, stirring, to cook off the excess moisture. Set aside to go cold.
2. Preheat the oven to 160°C/fan140°C/gas 3. Grease and baseline a non-stick 20cm springform tin with baking paper. Sift the flours, bicarbonate of soda, spices and sugar into a mixing bowl, plus any bran left in the sieve. Stir in the raisins and walnuts. Weigh out 550g apple purée and stir into the dry ingredients with the oil.
3. Spoon the mixture into the tin, level the top and bake on the middle shelf for 55-60 minutes, until a skewer pushed into the centre comes out clean.
4. Meanwhile, put the frosting ingredients – except the walnuts – in a bowl and beat until smooth. Cover and chill.
5. Take out the cake and cool in the tin for 10 minutes, then turn out onto a wire rack to go cold. Spread over the frosting, sprinkle with more cinnamon and decorate with walnuts.