01 -
Preheat your oven to 180ºC/160ºC fan and line a 9x13" traybake tin with parchment paper. Beat together the butter and sugar until light and fluffy. Add the eggs, self-raising flour, and vanilla extract, and mix thoroughly until combined.
02 -
Pour the batter into the prepared tin and bake in the oven for 45-50 minutes, or until fully baked (insert a skewer and ensure it comes out clean). Allow the cake to cool completely in the tin.
03 -
In a medium-sized bowl, mix the icing sugar with water gradually until it forms a thick paste.
04 -
Spread the icing evenly over the completely cooled cake.
05 -
Sprinkle rainbow sprinkles over the icing. Allow the icing to set for about an hour before serving.