Kumara, spinach & feta tortilla with sumac & yoghurt

There are really two tortillas in the culinary world. The Mexican corn- or flour-based wrap, and the Spanish potato, onion and egg omelette. To make it a little more confusing, the Italians have their frittata which in many ways is just like the Spanish tortilla, although you’ll find it made with the addition of spinach, cheese and other ingredients. For the sake of this chapter, as tapas make up quite a few of the recipes, I’ve called this a tortilla in honour of Spain - albeit a non-tradi