Preheat the oven to 350 degrees. Grease and line the base and sides of a 7 1/2 inch springform cake tin.
Sieve the flour and baking powder into a bowl, stir in the sugar, mashed peaches, walnuts, eggs, oil and carrots. Place the mixture into the lined tin, spreading evenly to the sides leaving a slight hollow in the centre. Bake for 50 60 minutes. Test by inserting a skewer into the centre, which should come out clean. Leave to cool on a wire cooling rack.
To finish the cake, cream the butter or margarine with the icing sugar until soft and fluffy. Cut the cake in half and spread the top half with some of the icing. Stir 2 [assionfruits into the remaining icing and use to sandwich the two halves together.
Arrange the peach slices round the top of the cake. Fill the centre with the pulp from the remaining passionfruit.