Heat the oil in a pan. Fry the peppers and onion until soft, about 10 mins. Add the beans, fajita spice mix, chopped tomatoes and some seasoning. Bubble for 5 mins to reduce the tomatoes a little, then stir in most of the coriander. Heat the grill and warm the tortillas in the microwave for 30 seconds.

Spread a quarter of the pepper and onion mixture over the base of an ovenproof dish (a round one, if possible) or frying pan. Top with some of the soured cream and a warm tortilla, then repeat the layers three more times, finishing off with a final layer of soured cream. Sprinkle over the cheese and grill for 5 mins, or until golden and bubbling. Scatter with the remaining coriander before serving.