Step 1

Preheat your oven to 180ºC/160ºC fan and line a 9x13" traybake tin with parchment paper.

Step 2

Beat together your butter and sugar until light and fluffy.

Step 3

Add in the eggs, self raising flour, and vanilla extract and beat again until combined well.

Step 4

Pour into the tin and bake in the oven for 45-50 minutes, or until baked through.

Step 5

Once baked, let the cake cool fully in the tin.

Step 6

Add the icing sugar to a medium sized bowl, and gradually add the water, mixing well each time, until a thick icing paste is made.

Step 7

Carefully spread the icing over the cake evenly.

Step 8

Sprinkle over your favourite rainbow sprinkles!

Step 9

Leave the icing to set for about an hour, and enjoy.