Thinly slice the cucumber and onion. Finely chop the tomato. Put 3 tsp red wine vinegar and 1 tsp sugar in a large bowl, season with salt and stir to combine. Add the cucumber and half the onion and toss well to combine. Set aside to pickle, tossing occasionally, until needed.
Step 2 — Brown chicken and onion
Thinly slice the chicken. Put the chicken and 1 tsp Mexican seasoning (see Make it milder) in a bowl, season with salt and pepper and toss to combine. Heat 2 tsp olive oil in a medium frypan over medium-high heat. Cook the chicken and remaining onion, stirring, for 2-3 mins until the chicken is browned and the onion is softened. Remove from the pan.
Step 3 — Make mojo sauce
Return the pan to medium heat. Add the tomato, 1½ tsp Mexican seasoning and 2 tbs tomato sauce and cook, stirring, for 30 secs. Add 125ml (½ cup) water and bring to the boil. Cook for 5 mins or until thickened.
Step 4 — Cook chicken
Reduce the heat to medium. Stir the chicken and onion into the sauce and cook for 3 mins or until the chicken is cooked through. Remove the pan from the heat. Taste, then season with salt and pepper.
Step 5 — Serve up
Meanwhile, put the tortillas on a plate, slightly overlapping, and microwave for 30 secs or until warmed through (see Kitchen notes). Spread the tortillas with the mayonnaise, top with the chicken mixture and drained pickled vegetables and enjoy!
Step 6 — Make it milder
We've suggested this amount of Mexican seasoning for flavour, but if you prefer less heat or have little ones, reduce the amount to taste. ~ Don't have a microwave? You can warm the tortillas, wrapped in foil, in a 220C oven for 8 mins or until warmed through. Or, warm the tortillas, in batches, in a frypan over medium-high heat for 30 secs each side.