Microwave the milk and margarine together until the margarine has melted. Add the eggs and castor sugar into a mixing dish and beat well until smooth. Add the flour slowly and mix. Add the baking powder until well blended. Add the melted buter and milk into the flour mixture together with the vanilla and mix well until you get a very smooth consistency. (I use my hands and it works perfect). Pour into a greased pan (any shape) and bake at 180 degrees for approximately 15 minutes and the cake will rise and be light brown. (Can be used for cupcakes as well.) Enjoy !!!