1) In a heavy-duty resealable plastic bag, combine 2 tablespoons of the vegetable oil, lemon juice, garlic, cumin, garlic powder, onion powder, hot sauce, salt, pepper and your choice of meat. Seal and toss the bag around to coat. Marinate in the refrigerator. Marinate 15 minutes for prawns, 20 minutes for chicken and 1 hour for skirt steak.
2) Preheat your cast iron servers in a preheated 200C/Gas 6 oven for at least 20 minutes, to get a good sizzle when you plate the fajitas.
3) Heat the outside barbecue or a large indoor griddle pan to medium-high heat. Remove the meat from the marinade and place it on the hot griddle, discard the marinade. Cook chicken until cooked through, about 5 minutes per side, skirt steak about 3 minutes per side for medium-rare and about 2 minutes for prawns. Slice the chicken and steak into strips, if you are using.
4) In a large skillet heat up the remaining 2 tablespoons of vegetable oil and fry the onions and peppers until crisp-tender with some salt and pepper.
5) Wrap the tortillas in aluminium foil and warm them in the oven with the servers for 15 minutes.
When you are ready to serve, remove the cast iron servers from the oven and quickly arrange the meat and peppers and onions on it. It will immediately start to sizzle from their fat and moisture. Immediately serve meat, sizzling, with the warm tortillas and other accompaniments.