Hi, I hope you can help.  I am making a cake in August for Icing Smiles.  The young lady I'm baking for has an illness where she can not process proteins or fats.  She has never been able to eat more than a bite or two of cake.

She loves banana bread cake.  

While I can't eliminate all proteins and fats, I was thinking I could substitute bananas for eggs and apple sauce for butter/oil in the cake.

Do you think this will work or do you have any suggestions? Cake chemistry in the works here!

Without any fat the cake is going to be dry and tough regardless. The applesauce will only work to a certain extent but regardless of what anyone says it's not a 100% fat replacer. My SIL makes a heinous chocolate cake with all applesauce then demands that I tell her it's great when it tastes like butt, so you shouldn't substitute all of the fats for applesauce.

I'd make a banana bread-type recipe instead of a cake, then maybe torte it into 1/2" layers and layer it with preserves. You might want to look into gluten-free recipes because the proteins in lour are what help create the structure of the cake, and if she can't eat that then you want to avoid wheat flour. There's both protein and fats in eggs so definitely don't use those. Dairy has protein in it so avoid that. Use an almond milk or a soy milk, but I don't know about the protein in those either. Yikes...

Thank you for the reply.

yikes is right!  The family is great and said don't worry, she is used to not getting to eat her cake, she just likes the photos but I hope to come up with something she can atleast have a small piece of.

How about a vegan cake ? Maybe some vegan recipes can help you 

Dang.   I'm surprised she was referred by Icing Smiles with those specific dietary restrictions.  I'd suggest you ask the family to contact her doctor/dietician or give permission for you to contact her doctor/dietician and ask them for a recipe.  There are WAY too many danger areas here to do this on just the family's 'ok'.  I would absolutely involve her medical team.

The doctor/dietician may have a recipe and then you could shape it, cover it with fondant (that could be removed if needed) and make it 'cute'. 

Personally, I wouldn't touch this without specific info from her medical team.  I worked for many years with special needs children and this is a scary area.

Wish you the best of luck.

Apti, I appreciate your input and yes, I've had those same concerns.  They did not list any dietary restrictions as the young lady just never eats any of her own cake.  Which just seems so sad to me.  Since I have time to explore and experiment and because I'm  doing a rather large, multi-tiered cake, I thought if I could come up with something, a recipe, then it could be run by her doctor before hand.

i have one advantage with this family...they live just about 4 miles from me and we are in a very rural area so I have had interactions with them before ever hearing about icing smiles. None of us would do anything to risk her health.