227g tin pineapple pieces, well drained and chopped (optional)
125g unsalted butter at room temperature
50g icing sugar
250g cream cheese
Heat the oven to 150C/fan 130C/gas 2. Line a 20cm, 10cm deep cake tin. Sift the flour, cinnamon, baking powder and bicarbonate of soda together and stir in the sugar. Beat the eggs with the oil and citrus zests. Stir in the carrots and fold everything into the flour mixture. Fold in the walnuts and pineapple if using. Spoon the mixture into the tin and bake for 1 hour 20 minutes or until a skewer comes out clean. Cool.
For the frosting, beat the butter and icing sugar together until soft and then beat in the cream cheese. Chill the mixture until it’s thick but spreadable. Spread a thick layer on top of the cake, making sure the side of the icing is flat and continues upwards from the side of the cake.