The only thing I can find is Imitation Butter & Nut flavoring. The person who requested the cake is allergic to whatever makes things imitation! So only natural ingredients can be used.

I recently picked up some Butternut for my Mom at a Kroger grocery store. I honestly do not know if anything was artificial or not because I did not look since I don't use it. Maybe your local Kroger has it also. Hope this helps.

I have a lorann flavoring oil in butternut, but I don't know if it has artificial ingredients.

Here's one from King Arthur flour: http://www.kingarthurflour.com/shop/detail.jsp?id=1748VANBUT

Not sure if it has artificial ingredients but you can call them up to ask.