This recipe from Nigella Express book uses a copper tart tatin dish which I don't have. Would I get the same results if I were to use a stoneware pie dish or should I rather consider investing in a proper tart tatin one?
Although you don't have to use a copper tart tatin pan for the clafoutis we do suggest that you use some sort of thin metal pan, such as a metal pie dish or a solid bottomed cake tin. The reason for this is that the batter in the clafoutis needs a fast blast of heat to help it rise and a metal container will heat up again quickly when it goes into the oven. Unfortunately a stoneware dish will take longer heat up, resulting in a flatter and possibly slightly soggy dessert.
You could use a cast iron ovenproof pan but as these are sturdier in construction than a tart tatin pan it will need to be preheated in the oven for slightly longer than the thin metal pan. We would suggest giving it 10-15 minutes in the oven before using. However as it has thicker walls than a tart tatin pan it will retain heat better when it is out of the oven and should still give you a puffy clafoutis.