This is so tough!! I feel so badly for various things like this, it is why I tried SO hard on all the social aspects(including food). I would think the best thing for your friend to do would be to call ahead, request the special pizza & ask that it be delivered with the party pizza...discretely!! If he is 35 however, there may be a way to reason through this one. Maybe start with a white pizza? alfredo sauce? bbq sauce? Yet, if this is his only food aversion & he doesnt want to change, so be it. We met a kid that couldn't have cheese on his pizza(among thousands of other things-think he ate like 3 things) 🤷♀️ I wish your friend luck in whatever they choose to do!!