What can you added to gluten free cakes to increase shelf life?

Found that cakes made with gluten free flour tend to turn dry in a day or two after being baked.

Please help.

My wife bakes delicious gluten-free cakes made with almond flour. They stay moist for several days, and have great shelf life. There’s a recipe here:

http://www.gluten-free-around-the-world.com/gluten-free-cake.html