Preheat the oven to 165 degrees C. Grease and flour a 23cm ring tin.
In a large bowl cream together the sugar and margarine until smooth. Beat in the eggs one at a time,then stir in the vanilla and lemon juice. Combine the flour, baking powder and salt; mix into the batter alternating with the milk just until blended. Pour into the prepared tin.
Bake for 1 hour in the preheated oven or until a toothpick inserted into the crown comes out clean. Cool in the pan for at least 10 minutes before inverting onto a wire rack to cool completely.