Preheat the oven to 220C, fan-forced, for the tortillas (or you can use a microwave if you prefer). Thinly slice the capsicum. Halve the carrot lengthwise and thinly slice. Finely chop the tomato and spring onion. Slice the chicken into strips.
Step 2 — Brown chicken
Heat 2 tsp olive oil in a medium frypan over high heat. Cook the chicken, stirring regularly, for 2 mins or until golden (the chicken won't be cooked through). Remove the chicken using a slotted spoon, leaving any flavoured oil in the pan. Reserve the pan.
Step 3 — Warm tortillas
Enclose the tortillas in foil. Put in the oven for 8 mins or until softened and warmed through. (To microwave, just before serving, put the tortillas on a plate, slightly overlapping, and microwave for 30 secs or until warmed through.)
Step 4 — Start filling
While the tortillas are warming, heat the reserved pan over medium heat. Cook the capsicum and carrot, stirring regularly, for 3 mins or until softened. Add the Tex-Mex seasoning and half the tomato paste* and cook, stirring, for 30 secs or until combined and fragrant.
Step 5 — Finish filling
Add 125ml (½ cup) water to the capsicum mixture and bring to a simmer. Cook, stirring occasionally, for 2 mins or until slightly reduced. Add the chicken and cook, stirring occasionally, for a further 2 mins or until cooked through. Taste, then season with salt and pepper. Remove the pan from the heat.
Step 6 — Make salsa and serve
Meanwhile, combine the tomato, spring onion, 1 tsp extra virgin olive oil and ½ tsp red wine vinegar in a bowl and season with salt and pepper. Divide the tortillas among plates, then fill with the chicken filling and salsa. Scatter with the cheese and a pinch of chilli flakes*, if desired, then fold in half to serve.