Grease and sugar or flour a 10 inch tube pan or 12 cup bundt pan.
Preheat oven to 350 degrees F.
Sift flour, baking powder, and salt.
In the bowl of an electric mixer, cream butter, shortening, and sugar.
Add eggs one at a time beating until the yellow is incorporated before adding the next egg.
With the mixer on low, add dry ingredients alternating with the heavy cream and milk. (Add 1/3 dry ingredients, add heavy cream, add 1/3 dry ingredients, add milk, add last 1/3 dry ingredients.
Mix in lemon juice and zest.
Spoon into prepared pan.
Bake 55 to 65 minutes.
Cool on wire rack for 20 minutes before inverting on a serving tray.
Cool completely before covering.