Unadon (鰻丼?, an abbreviation for unagi + donburi, lit. "eel bowl") is a dish originating in Japan. It consists of a donburi type large bowl filled with steamed white rice, and topped with fillets of eel (unagi) grilled in a style known as kabayaki, similar to teriyaki. The fillets are glazed with a sweetened soy-based sauce, called tare and caramelized, preferably over charcoal fire. The fillets are not flayed, and the grayish skin side is placed faced down. Sufficient tare sauce is poured over so that some of it seeps through the rice underneath. By convention, pulverized dried berries of sanshō (called Japanese pepper, although botanically unrelated) are sprinkled on top as seasoning.
Variations include unajū (鰻重, the same dish served in jūbako [重箱], food boxes often lacquered), nagayaki (長焼き, the eel and rice are served separately), and hitsumabushi (櫃まぶし).
There are two styles of grilled eel, the topic of which is covered more precisely under kabayaki. Essentially, in the Kantō region style, the eel is steamed before being grilled with sauce, which makes the eel more tender. The other is the Kansai region style, which is grilled without steaming.
Una-don was the first type of donburi rice dish, invented in the late Edo Period, during Bunka era (1804-1818) by a man named Imasuke Ōkubo  of Sakai-machi (in present-day Nihonbashi Ningyōchō, Chūo-ku, Tokyo), and became a hit in the neighborhood, where the Nakamura-za and Ichimura-za once stood.
The first eatery to sell it as a business is claimed to be Ōnoya (大野屋?) , in Fukiyachō (葺屋町?) (adjacent to Sakai-chō) at some indeterminate time, but presumably before the theaters burnt down in 1841 and moved off. After the great famine of 1844, it started selling the unadon for one oblong Tenpō-sen coin, and became a hit.
As for unajū, where the eel and rice is stuffed in jūbako boxes, one theory ascribes its originator to one Gihei (大谷儀兵衛?), who started a freshwater fish restaurant business in Sanya, Asakusa, Tokyo called Funagi (鮒儀?) (later known as Jūbako, the current generation of the restaurant is in Akasaka). According to this version the unajū was already around by late Edo period, but there are detractors to this view. Other commentators say unajū appeared in the Taisho era, and by using lacquered boxes, aimed at appearance of luxury. Unajū is usually pricier than unadon.
|Wikimedia Commons has media related to Unadon.|
- Richie, Donald (1985). A taste of Japan: food fact and fable : what the people eat : customs and etiquette. Tokyo: Kodansha International. ISBN 9784770017079., p.63
- Barber, Kimiko; Martin Brigdale (photos) (2004). The Japanese Kitchen: A Book Of Essential Ingredients With 200 Authentic Recipes. Tokyo: Kyle Books. ISBN 9781904920021. , p.144-
- The East 1991, section "Una-don, the First Donburi-mono", p.24-
- Mori, Senzō (森銑三) (1969) . 明治東京逸聞史 2. Heibonsha., p.270, quote;:"鰻丼を始めたのは日本橘葺屋町の大野屋で、天保の飢饉当時に、大丼の鰻飯を天保銭一枚で売ったのが当って"
- 多田, 鉄之助 (1972). たべもの日本史 1. 新人物往来社., p.?, the author claims to have heard from the current successor to the restaurant that it was not the original innovator to put eel in jubako, and the old restaurant in Sanya was so named because the architecture resembled the jubako boxes
- うな重とうな丼、違いは名前と器だけ (Excite News, 22 July 2007; author: Wakako Tasachi (田幸和歌子)
- The East (Nov–Dec 1991). "Donburi-mono". The East 27: 24–.