OK, so I love a culinary challenge and am happy (on occasion) to cook for friends with food fads. However, I have an interesting one in a new friend who is allergic to onion. I thought that wasn't to big a deal, until I realised quite how much of what I cook contains onion. Onion is not normally a big part of most meals, but it is vital to flavour and not easily substituted.
So, what would you recommend?