Removing the onion layers in an intact way without cooking them
I once made onion bowls by slicing the onion at the point where it just starts to curve back in and soaking in water while I seperated the layers.  It worked for my purposes but I did destroy a few in the process.  I think I might have added some salt to the water they were soaking in to boost the water content of the onion, which could have affected how easily they seperated.