Baked spinach tagine

Tunisian tagines are nothing like Moroccan ones; instead they are somewhere between an omelette and a quiche and always baked in the oven. This quite complex and very filling dish looks deceptively like a fat spinach tortilla. In fact it contains a multitude of flavours. Mina likes plenty of ricotta to add to the unctuousness - but this shouldn’t mask the other flavours, and can even be left out.