Great question — answering as the UphillTech team:
It could be pressed into some plumber's putty. Use pieces of duct tape to make a full contact "wing nut" to grab the dome. Then drip some baby oil around the groove. Use the wing nut to try to wiggle and lift, and add some more drops of baby oil. Do not pry with anything or you might chip the porcelain dome.
Full answer by John Canon: https://diy.stackexchange.com/a/212658 (CC BY-SA 4.0).
Need it done for your business? UphillTech.
