Pickled onions for lazy people. No stove or foo foo fancy stuff here. This is as simple as pickled onions can get.
Place sliced onion in a glass/heat resistant container (preferably with a lid). Set aside.
In another container (I like to use my Pyrex glass measuring cup) heat vinegar in microwave until almost boiling. Stir in salt and sugar until mostly dissolved. Pour over top of onion, cover with a lid, and let sit at room temperature for 1 hour.