Preheat oven 180°C.
Line a muffin tray with 12 cupcake cases.
In a large bowl mix together the flour, sugar, baking powder and salt.
Pour vegetable oil into a jug, add the warm water and vanilla extract, then whisk together.
A quarter at a time our the wet ingredients into the dry, whilst whisking until all combined and you have a smooth batter.
Now pour the batter into a disposable piping bag, snip off the end and use that to fill each cupcake case until half full (you’ll find this technique a lot easier & less messy, than using an ice-cream scoop or spoon).
Bake for about 18-20 minutes, or until a cocktail stick poked in one comes out clean.
Remove from the oven and remove from tray, then place on cooling rack to cool completely.
Meanwhile, in a bowl whisk together the icing sugar, butter and vanilla extract until combined. Then add in a few drops of your chosen food colouring and whisk until smooth.
Fill a disposable piping bag, with tip of your choice already in (I used a Wilton 1M tip to get the 'Rose' swirl effect), with the butter cream and pipe on to your cupcakes.