Preheat the oven to 180C/160C (fan)/Gas 4. Grease and line a 20cm/8in square loose-bottomed cake tin.
Place the flour, sultanas, pecans, orange zest, cinnamon, grated nutmeg, baking powder, bicarbonate of soda and salt in a large bowl and mix until well combined.
Beat the eggs until smooth. Add the sunflower oil and sugar and whisk until well combined.
Make a well in the centre of the flour mixture and beat in the egg mixture until smooth. Stir in the carrots. Pour the mixture into the prepared cake tin and smooth the surface. Bake in the centre of the oven for 35-40 minutes, until the cake is well risen and feels springy to the touch. (Test the cake by inserting a skewer into the centre. If the skewer comes out clean, the cake is done.)
Remove the cake from the oven and set aside to cool in the tin for five minutes. Remove the cake from the tin and set aside to cool on a wire rack.
For the icing, sift the icing sugar into a large bowl and add the butter and orange juice. Beat together with a large wooden spoon until light and creamy. Add the cream cheese and orange zest and beat until smooth. Cover and chill in the fridge for 30 minutes or until firm enough to spread.
Spread the icing over the cake and sprinkle with the pecans. Cut into squares to serve.