1: Lay the tuna in a shallow tray and sprinkle with the chilli flakes, oregano, lime zest and salt on both sides. Trickle with the olive oil and turn the fish to coat well all over. Set aside in a cool place to marinate for an hour or so.
2: Meanwhile, to prepare the radishes, put them into a small bowl, sprinkle with a little salt and squeeze over the lime juice. Mix well and leave to pickle for an hour.
3: For the pineapple salsa, mix all the ingredients together in a bowl and set aside.
4: For the avocado crema, halve, peel, de-stone and chop the avocados then place in a blender or food processor with the soured cream and chipotle. Blitz until smoothly combined. Transfer to a serving bowl.
5: When you’re ready to cook, lay the tuna steaks directly on the barbecue and cook for 1 minute on each side. Remove to a tray and leave to rest for a couple of minutes.
6: Meanwhile, place the tortillas on the barbecue for around 10 seconds on each side until warm and lightly charred but still pliable. Slice the tuna steaks.
7: To assemble the tacos, spread a spoonful of avocado crema on each tortilla and scatter over some shredded red cabbage. Add a couple of tuna slices and top with a spoonful of pineapple salsa and some pickled radish slices. Serve with lime halves for squeezing over.