Short answer
A tiny amount won't poison them, but citrus often upsets cats' stomachs. Kittens are extra sensitive due to their small size and developing digestion. Watch for drooling, vomiting, or diarrhea in the next few hours. Skip the peel entirely — the oils there cause more irritation. If they seem off, call your vet to be safe.
Tangerine — Food safety facts
Feed with care · Cats · full breakdown on the linked food page
Same as other citrus — the essential oils in the peel cause stomach upset.
The full verdict, portion guidance and serving notes are collected on the Tangerine food facts page.