Grease and flour a 10" tube pan or bundt pan. Set oven at 350 degrees.
Cut butter and shortening into dry ingredients. Add eggs, all at once, mixing only until well blended. Add 1/2 of milk. Beat on medium speed of mixer for 3 to 5 minutes, scraping sides of bowl often. Add rest of milk, vanilla, lemon juice and zest. Mix only until blended. Pour into prepared pan and bake for 1 hour or until done. Cake is done when it pulls from sides of pan. Cool on wire rack for 5 minutes and then turn pan over. Sprinkle with powdered sugar before serving.