Wirecutter doesn’t specifically say boil but it uses the same time that all the other sources do, which is 5 minutes. In my experience, two cups of water will easily boil in 4.5 minutes in most microwaves (cheap potatoes), so there you go. Vinegar or lemon juice isn’t far from water’s boiling temperature.
Wait until you find out how steam works
I’m just going by 100% of the instructions online, which all say “until it boils.”
Southern Living, The Kitchn, The Spruce, Good Housekeeping all say “boil”
Wirecutter doesn’t specifically say boil but it uses the same time that all the other sources do, which is 5 minutes. In my experience, two cups of water will easily boil in 4.5 minutes in most microwaves (cheap potatoes), so there you go. Vinegar or lemon juice isn’t far from water’s boiling temperature.