You will need: 175g self raising flour, 175g caster sugar, 175g margarine, 3 eggs-beaten, 1/2 teaspoon vanilla extract.
Set the oven to 180C and prepare two round (or one large) tin by greasing and dusting with flour. Using an electric whisk, cream the butter and sugar until light and fluffy, then gradually add the beaten eggs and vanilla, still whisking so that the result it smooth and fairly pale. Sift in the flour and fold in with a metal spoon until thoroughly mixed. Spoon into the tin and bake for about 25 minutes so it is golden and a skewer comes out clean.