If you can find pre-cooked vacuum packed beetroot, they would make an acceptable substitution in this tarte tartin. Use whatever cheese you prefer; feta, Persian feta or goat cheese. I use a 20cm cast iron fry pan to make this tart, which will feed the three of us for dinner with a good side salad and maybe some crusty bread. You can make a larger tart if you wish, just scale the ingredients up accordingly. Don't make it too large though or it will be difficult to turn out of the fry pan.