Stir flour, cream of tartar, salt, and mace together. Cream butter thoroughly; gradually add sugar, a small amount at a time, creaming well. Beat in eggs, one at a time, beating well after each. Stir in vanilla. Add dry ingredients, gradually, mixing only until thoroughly blended. Pour batter into a greased and floured 8 1/2" by 4 1/2" by 2 1/2" loaf pan. Bake in a moderate oven 325°F 60 to 70 minutes or until done. Sprinkle top with icing sugar or serve plain.