Preheat oven to 180°C/fan 160°C/gas mark 5.
Cream together the sugar and butter in a bowl.
Add the Fate Low Protein All-Purpose Mix and baking powder and rub together with your hands until it resembles breadcrumbs.
In a separate bowl, mix together the ProZero, egg replacer and vanilla essence.
Add the ProZero mixture to the breadcrumb mixture and mix until well combined.
Add in the food colouring until you achieve the colour you desire.
Spoon the mixture evenly into the cupcake cases and bake in the centre of the for 25 minutes.
Remove from the oven and allow to cool.
In a bowl mix the food colouring into the icing and spoon into a piping bag.
Ice the cupcakes and add the rainbow belts to form an arch.
Add the Skittles around the base of the rainbow and serve.
Fate Low Protein All-Purpose Mix and ProZero are foods for special medical purposes and must be used under medical supervision.