I don't know why the French have recently started talking about a tajine. By the way, this is a very specific problem that English people do not even imagine, in this blessed language where all objects are "it". In French, Spanish, etc. objects have a genre, can be feminine or masculine.. UN or LE is the article for masculine, UNE or LA for feminine nouns.
So, now, let me rant in English about a French mistake…
Sorry, but they say UN tajine. Male word.
LA Tanjia, a dish and a container, too

Okay, in French, cooking utensils and the dishes you cook in them are often feminine: unE casserole, unE poêle, unE marmite.
In Moroccan, we say unE tangia — which is a dish cooked in a pot -, but uN couscous — made in a couscoussière — and especially uN tajine.
In French we say uN grill and possibly unE grillade. A stew, in a casserole or a stewpot…
So if you absolutely have to be feminine, be nice and tell me about a good tajinADE, cooked for a long time in a tajine.
By the way, where does the tagine come from?
This earthen dish, hollow but not very deep, topped with a conical lid, is very old.
Its name is a Berber word, ⵟⴰⵊⵉⵏ, which was later taken over in Arabic (as couscous).
Like the Provençal word "tian" (also masculine, I'm just saying), its etymology can be traced back to the ancient Greek têganon ( τήγανον ), which designates a frying pan, a dish, a bowl, in short, a thing exactly like the tajine. The tian has lost its lid, but it also designates both the utensil and the dish cooked in it.

The very first tagines are mentioned in the Arabian Nights, and the very first recipe using a tagine dates from the Middle Ages. Ibn al Adim, a Syrian historian and diplomat, took the calamus for a treatise on "perfumes" which includes cooking:
Boil and fry the meat with fresh coriander, onions, hot spices and a little garlic. Then take the fennel bulbs and cut them in half. Place them on top of the meat. Put some of the stock back in with the tail of the mutton. Simmer until the meat is cooked and the stock is absorbed.

With the exception of the use of fennel, which is very rare in Morocco, nothing has changed.…
Very different recipes under a single name
Used throughout the Maghreb — but particularly in Morocco — the tagine is used to cook very different dishes. You wouldn't say "this is a recipe for a pot", because there are so many different things you can put in it. It's the same with a tagine.
A tagine is a slow cooking, stewed, of an assortment of vegetables accompanied — or not — by meat, fish, eggs. The onion is almost always part of it, as it adds flavour by providing moisture. It is placed on a brazier, coals or a kanoun. Or on gas for modernity!
In Tunisia, on the other hand, it is used in the oven to cook some kind of quiches or fritattas, which can be wrapped in sheets of brick, without its pointed lid!

Are you in love with a tagine? Here are all the tips you need to choose and use your tagine.