Preheat oven to 350F.Spray or butter and flour 2 loaf pans or one large Bundt pan.
Sift flour, baking powder and salt into medium bowl. Set aside.
Using an electric mixer, cream together butter, shortening and sugar.
Add eggs one at a time, beating until well blended after each one.
Add dry ingredients in three additions to butter mixture alternately with milk, beginning and ending with flour mixture.
Beat at low speed just until blended after each addition.
Mix in lemon juice and zest.Pour batter into prepared pans.
Bake cakes until tester inserted into centre comes out clean, about 55 minutes.
Cool cakes in pans for 15 minutes. Turn cakes out onto racks and cool completely.