No water. From memory, you get a pan really hot to the point where a drop of water will bead up and roll around, then drop in the onion slices. Here’s where I get foggy, but you’re just supposed to leave it there for a long time, slowly lowering the temperature of the pan then flip the slices over. I’ve scoured so many pans with The Barkeeper’s Friend that I can’t bring myself to try this for fear of needing an angle grinder to clean the pan.