Heat oven to 180C/160C fan/gas 4. Grease and line a 22cm square tin with baking parchment. Whisk the oil and sugar in a large mixing bowl until light and fluffy. Beat in the eggs, one at a time, followed by the banana. Stir through the apples, carrots, mango and lemon zest. Combine the flour, bicarb and mixed spice in another bowl, then fold into the fruit mixture.
Pour the mixture into the tin and bake for 40 mins, until a skewer inserted comes out clean. Cool for 10 mins before turning out onto a wire rack.
To make the icing, beat together the icing sugar, passion fruit or lemon curd and the cream cheese. Spread over the top of the cake and cut into square pieces to serve.