This simply-decorated ceramic teapot radiates transmutation magic. It has a wide opening at the top with a tight-fitting lid, and its steel lining has a regular pattern of small perforations to strain liquid as it pours out the spout. These commonly appear as part of a wealthy family's everyday tea service, usually with 6 matching teacups and saucers.
When the teapot is filled with water (other liquids will not work) and the lid is turned clockwise until it clicks, the metal lining begins to heat rapidly as if by a heat metal spell. Turning the lid counterclockwise will stop the effect immediately. The heat lasts for 1 minute, which brings the water to a boil. Add loose tea immediately after the boil, and steep for the recommended time before pouring. For lesser amounts of liquid, steam escapes through a hole in the lid causing a piercing whistle which rotates the lid counterclockwise to stop the heat early.
In the creation process, the steel lining gets worked on its own before the ceramic adheres to it. The ceramic exterior gets a little warm, but it insulates the water within and keeps it warm for at least an hour. Most versions also have an additional feature. When filled with water, turn the lid counterclockwise until it clicks. The lid will unlock with a click 10 minutes later after ritually casting purify food and drink on the contents of the teapot. Sellers in Fellport tout this ability as "civilization in the wild", allowing the owner to enjoy a safe cup of tea under the worst travel conditions.
Note: This idea isn't mine, though I'm frustrated I didn't come up with it on my own. I tripped across this Pandora's Cubicle YouTube short entitled "Tea Time Ritual" by @ToBinge, and I felt a mighty need to include it in Fellport. Incidentally, I have now binged my way through every published video, and I recommend you do the same. The animation style is spot on, the music and references fit perfectly, and the worldbuilding via vignette fills me with glee. If you want to use a bell as the trigger and summon anthropomorphic sheep druids to heat your water with this item, I'm totally coming to your place for tea.