I can help with the gluten free part, but I'm unsure of the diabetic requirements. I have posted a recipe under "special diets" for a GF fudgy chocolate cake. (if I was clever I would insert a link to the recipe, but I'm on my iPad and don't know how to do it ) it uses chick peas instead of flour. Don't let that put you off though as it results in a moist chocolatey cake that tastes nothing like chick peas. It does have 2/3 cup of brown sugar. I think you could adjust it to 1/2 cup and use the logical cane sugar which is lower GI, or an artificial sweetener like Splenda. Someone more knowledgable than me can probably give better advice about the sugar component. Good luck!Here's the link