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. *Cook's Note: 15 minutes for shrimp, 20 minutes for chicken and 1 hour for skirt steak.
Preheat your cast iron servers in a preheated 400 degree F oven for at least 20 minutes, to get a good sizzle when you plate the fajitas.
Heat the outside grill or a large indoor grill pan to medium-high heat. Remove the meat from the marinade and place it on the hot grill, 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 shrimp. Slice the chicken and steak into strips if you are using.
In a large skillet heat up the remaining 2 tablespoons vegetable oil and fry the onions and bell peppers until crisp-tender with some salt and pepper.
Wrap the tortillas in 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. Serve sizzling immediately with the warm tortillas and other accompaniments.