Heat the oil in a large frying pan. Fry the onion and half the chilli for 5 mins until softened. Tip in the spices, fry for 1 min more, then add the cherry tomatoes, potatoes and coriander stalks to the pan. Season the eggs well, pour over the top of the vegetables and leave to cook gently for 8-10 mins until almost set.
Heat the grill and flash the tortilla underneath for 1-2 mins until the top is set. Scatter the coriander leaves and remaining chilli over the top. Place the egg covered veggies on top of the tortilla. Remove from heat and slice into wedges.