Preheat the oven to 350°F.
In a bowl, combine the butte, caste sugar, vanilla extract, eggs, flour, baking powder and milk; stir it until well blended.
Pour batter into cupcake liners until they are 2/3 full.
Place into the preheated oven and bake it for 12-15 minutes.
Take cupcake out from oven and let it cool completely.
For the topping, stir the icing sugar with the water. And then, add in the food colouring.
Topping the icing on the cupcakes and store it into refrigerator.