Don't preheat the oven. Grease and flour a 10-inch tube or Bundt pan. Sift together the all-purpose flour and self-rising flour; set aside.
In a large bowl, cream together margarine, shortening, and sugar until light and fluffy. Beat in eggs one at a time. Then beat in flour mixture and milk, mixing just until incorporated. Finally, stir in lemon extract and vanilla.
Pour batter into a 10-inch tube or Bundt pan. Place cake in a cool oven and set the oven to 350 degrees F (175 degrees C). Bake for 1 hour and 15 minutes, or until a toothpick inserted in the center comes out clean.