Preheat the oven to 200C / 395F / 180C fan forced.
Strain the crushed tomatoes into a bowl, pressing through with a spoon, until you have just ½ cup of pulp left. Reserve the purée for something else, you only need the tomatoes for the nachos.
Mix the fajita seasoning ingredients (paprika, cumin, garlic powder, onion powder, chilli powder and salt) together in a small bowl.
In a cold non stick frying pan, combine the chicken thighs, spice mix and 3 teaspoons of oil. Mix well until the thighs are evenly coated.
Place pan over medium heat and cook for 4-5 minutes. Flip then cover for another 4-5 minutes or until cooked through (notes 2). Transfer chicken to a bowl with all the juices.
Add the remaining teaspoon of oil to the pan, along with the capsicum and onion. Cook for 3-4 minutes until softened. While that’s cooking, slice the chicken into small pieces.
Add the tomato pulp to the pan with the vegetables, then cook, stirring, for a minute to evaporate any remaining juice.
Add the chicken along with any juices from it and give it a stir to combine everything well. Take it off the heat.
Place half of the chips into an 9 inch round casserole dish or skillet - slightly overlapping and some sticking up around the sides.
Set aside ⅓ of the cheese for topping. Scatter ⅓ of the remaining cheese over the chips. Add half the chicken mixture and another ⅓ of the cheese. Repeat - corn chips, cheese, chicken topping it finally with the cheese you set aside. This puts the largest cheese portion on the top.
Bake for 10 minutes or until cheese is melted and bubbly
Serve immediately, topped with jalapeños and coriander over the top and guacamole and sour cream on the side.
Paprika - I like mild or sweet but use smoked if you prefer
Internal temperature of cooked chicken is 75C / 165F