Preheat the oven to 220C, fan-forced. Line an oven tray with baking paper. Thinly slice the onion with a sharp knife or mandoline. Peel the cucumber into ribbons with a vegetable peeler. Pick the coriander leaves and finely chop the stems. Finely grate the zest of half the lime, then juice the half. Cut the remaining lime into wedges.
Step 2 — Cook pork
Drizzle the pork with 2 tsp olive oil and season with salt and pepper. Heat a large frypan over high heat. Cook the pork, turning, for 4 mins or until browned. Transfer to the lined tray and spoon over the chipotle (see Make it milder). Roast on the top oven shelf for 11-13 mins until cooked to your liking. Remove from the oven and rest for 5 mins.
Step 3 — Pickle onion
Meanwhile, combine the lime zest, lime juice and 2 tsp sugar in a large bowl. Add the onion and coriander stems and toss to combine. Set aside to pickle, tossing occasionally, until needed.
Step 4 — Warm tortillas
Enclose the tortillas in foil. Put in the oven for 8 mins or until softened and warmed through.
Step 5 — Serve up
Add the cucumber to the onion mixture and toss to combine, then drain, discarding the pickling liquid. Slice the pork. Divide the tortillas among plates and top with the cucumber mixture and pork. Drizzle with the mayonnaise, scatter over the coriander leaves and serve with the lime wedges. Enjoy!
Step 6 — Make it milder
Chipotle is a smoky Mexican condiment with a chilli kick, so reduce by half (or more) if you aren't a big chilli fan.