Preheat oven to 180c and prepare a grease cake pan.
In a medium sized bowl sift together the flour, sugar, cacao powder, baking powder, baking soda and salt. Set aside.
In a large bowl, mix the milk together with the oil, eggs and vanilla. Mix in the dry ingredients in the wet ingredients and the water, but do not over mix. You will notice that the batter is very thin.
Pour the batter into the prepared cake pan, and bake for 50-60 minutes or until a toothpick comes out clean from the centre of the cake.
To make the frosting, beat the butter with the caster sugar, cream and vanilla (or orange extract). Add in food colouring and mix very well. You can also add salt to taste.
Let cake cool down completely before getting in out. After you get it out, cut it in half, soak each half with 1/2 cup of orange juice and frost it.