Combine the lime juice, chilli powder, oregano, coriander and black pepper in a medium bowl.
Place the steak in a shallow bowl and spoon 2 tablespoons of the lime mixture on top; turn to coat both sides. Leave to stand while you grill the vegetables.
Preheat the tawa or grill to moderate high. Wipe a little olive oil on a pan and place the onions and pepper pieces, skin-side up, on the pan. Cook/grill for about 10 minutes or until the peppers are charred and the onions are golden brown. Remove. When cool enough to handle, peel the peppers and thickly slice. Add the peppers and onions to the remaining lime juice mixture together with the fresh coriander and toss.
Grill the steak for about 4 minutes on each side or until cooked to your taste. Leave to rest for 5 minutes before slicing thinly. Grill the tortillas for about 15 seconds on each side or until lightly browned.
Place the sliced steak, peppers and onions, lettuce, curd and flour tortillas in serving containers. Let each person fill his or her own tortilla.
Some more ideas
*Use 2 skinless, boneless chicken breasts, 140g each, in place of the steak. Slice the chicken into 1cm (½in) strips and, instead of grilling, sauté in 2 tsp olive oil for about 5 minutes or until cooked through. *Use orange or yellow peppers rather than red. *Roll up the meat mixture in large lettuce leaves instead of tortillas.
*The vegetable mixture for these fajitas provides more than twice your daily requirement for vitamin C. This important vitamin works as an antioxidant to fight off a wide range of diseases. *Olive oil is rich in monounsaturated fats and is believed to be partly responsible for the low rates of heart disease and stroke in people in Mediterranean countries. Several studies have shown that replacing saturated fat with olive oil helps to reduce high blood cholesterol levels.