1. Start oven, set at Moderate, 325° F. Rub 2 loaf pans with margarine or shortening and line with heavy waxed paper.
2. Beat the butter or margarine until soft; gradually add the sugar and beat until creamy. Add the eggs, 1 at a time, beating well after each addition; beat in the vanilla.
3. Sift the flour with the mace, cream of tartar and salt and gradually add to the creamed mixture, beating thoroughly after each addition.
4. Pour the batter into the prepared pans. Bake about 1 hour.