Neutral cooking oilsuch as vegetable or rapeseed oil
Optional toppings such as sliced avocado, guacamole, sour cream, salsa, cheese, or refried beans
To begin, cut the chicken pieces into roughly equal-sized strips and add to a large mixing bowl alongside the smoked paprika, ground cumin, chilli, cinnamon, dried oregano, and a generous pinch of salt. Mix until combined, then add a healthy splash of cooking oil. Mix again and leave to marinate for 20-30 minutes.
While the chicken is marinating, roughly slice the onions and de-seed the peppers and cut into strips.
Heat a cast-iron skillet or large frying pan until screaming hot and add the onions. Cook for 2-3 minutes, turning often, until lightly coloured, then transfer to a large saucepan and continue to cook over low heat, stirring often.
Add the peppers, skin-side down, to the hot skillet and cook over high heat until the skin blisters. This should take 2-3 minutes. Turn the peppers over and continue to cook for a minute or two.
Add the peppers to the saucepan with the onions and add 2 teaspoons of sugar. Increase the heat and stir often for a minute until the sugar dissolves and the onions and peppers begin to caramelise. Add a splash of water to deglaze the pan and continue to cook on high heat until the water dissolves. Once dissolved, reduce the heat to its lowest setting.
While the water is dissolving, add the chicken to the hot skillet and cook for around 5-6 minutes over high heat, turning just once or twice. To check the chicken is cooked, tear in half at the thickest part of a thigh piece and if any part is still raw cook, until done.
Once the chicken is almost cooked, return the peppers and onions to the skillet. Decrease the heat and continue to cook while you warm the tortillas.
In a separate pan, warm the tortillas for 15-20 seconds on each side then eat as quickly as possible, filling the fajitas with the chicken-onion-pepper mixture and optional toppings such as sliced avocado, guacamole, sour cream, salsa, cheese, or refried beans.