Preheat your grill or oven. If using a grill, heat it to medium-high (about 200°C). If using an oven, preheat it to 200°C (fan-assisted) or 220°C (conventional). While it heats, prepare four large sheets of heavy-duty aluminium foil, each about 30cm long.

Prepare the chicken and vegetables. Slice the chicken breasts into thin strips, about 1cm wide. You want them uniform so they cook evenly. In a large bowl, combine the chicken strips, sliced bell peppers, and red onion. The peppers should look vibrant and the onion translucent white with purple edges.

Make the fajita seasoning. In a small bowl, whisk together the olive oil, lime juice, cumin, smoked paprika, garlic powder, onion powder, cayenne (if using), salt, and black pepper. The mixture will smell earthy and slightly smoky, with a sharp citrus note from the lime.

Toss everything together. Pour the seasoning mixture over the chicken and vegetables. Use your hands or a spatula to toss until every strip of chicken and every piece of pepper is coated. You should see a rich, reddish-brown colour from the paprika clinging to everything.

Assemble the foil packets. Divide the chicken and vegetable mixture evenly among the four foil sheets, placing it in the centre. Fold the foil over the filling, then crimp the edges tightly to create a sealed packet. Make sure there are no gaps — you want the steam to stay inside. Gently shake each packet to spread the ingredients in an even layer.

Cook the packets. Place the packets on the grill grates or on a baking sheet in the oven. Cook for 20-25 minutes. Halfway through, you might hear a gentle hissing sound as the steam builds inside. After 20 minutes, carefully open one packet (watch out for the hot steam!) to check the chicken. The chicken should be opaque all the way through and the peppers should be tender but still have a slight bite. If the chicken is still pink in the centre, reseal and cook for another 3-5 minutes.

Rest and serve. Remove the packets from the heat and let them rest for 2-3 minutes. This allows the juices to redistribute. Carefully open the packets — the steam will smell intensely of cumin and lime. Serve the filling directly from the foil or tip it onto a plate, accompanied by warm tortillas and your favourite toppings.