If the restriction is due to dietary concerns, do a search on 'celiac spru',
this is a disease that causes an intolerance to gluten (i.e. wheat flours).
You will find a wealth of sites that have recipes, and advice on what to use
Unfortunately I found that just one of the substitute flours does not really
work that well, but a combination helps get the right consistency. Never
exactly the same as wheat flour, but if your friend has been struggling with
this for any time they will already know of this limitation.
I had a similar experience and was able to make a delicious cake using rice,
potato (?), and tapioca flour. The tapioca was the key in the recipe I
found. Sweet white rice flour was better also than just the rice flour.
Have not had to do this in about two years, but just a quick search a moment
ago resulted in 3,532 matches.
Hope this helps.
Joseph A. Bonaiuto S.P.A.
Fingerhut Companies, Inc.
Professional Services Group