Grease and flour a tube pan.
Cream butter, shortening, and sugar.
Add eggs one at a time, beating well after each egg added.
Mix in the vanilla and the milk.
Sift in the dry ingredients.
Pour mixture into pan and place on low rack in a cold oven.
Bake at 325 degrees for 1 1/2 hours.
If you want a glaze, just mix 1 1/4 cups powdered sugar, 2 tsp lemon juice, and 1 to 2 tbsp milk, and pour over top of the cooled cake.