Grease and flour a 20cm round or square cake pan.
Beat margarine until light and fluffy then add in eggs one at a time, beating well after each addition.
Beat in condensed milk and add essence. Fold in sifted flour and mix well to blend to a batter-like consistency.
Turn out batter into prepared pan. Steam over high heat for 30 minutes. Reduce the heat to medium then continue to steam for a further 15 minutes or until cake is cooked (test with a skewer).
Remove cake out and cool on a wire rack.