Tuna Tataki with Avocado & Ponzu

Ingredients

• 300 g sushi-grade tuna loin
• Steamed jasmine rice, to serve
• 0.5 cucumber, thinly sliced
• 2 spring onions, finely sliced
• 1 red chilli, finely sliced
• 2 tbsp soy sauce
• 1 tbsp vegetable oil
• 1 tsp sesame oil
• 1 tbsp sesame seeds, mixed black and white
• 1 ripe avocado, sliced
• 2 tbsp yuzu juice or lemon juice
• 1 tbsp mirin
• micro herbs or coriander, to finish

Method

1. Whisk the soy sauce, yuzu or lemon juice, mirin and sesame oil together in a small bowl. Taste it — most of the salt comes from the soy, but if it reads flat, a tiny pinch ties it together. Set aside; this is your ponzu.
2. Pat the tuna loin bone dry with kitchen paper. Water means steam, and steam means no crust. Season the tuna generously with salt and pepper on all four long sides, then roll it firmly in the sesame seeds, pressing so they coat every face evenly.
3. Heat the vegetable oil in a heavy stainless or cast iron pan over the highest heat your hob will give until it shimmers and just begins to smoke, about 2 minutes. A non-stick pan won't hold this heat — you need a proper searing surface for the sesame to toast rather than steam.
4. Lay the tuna in the pan and sear for 30–45 seconds on each of the four long sides. You're after a thin, fragrant sesame crust the colour of pale gold and a vivid raw ruby centre. Don't be tempted to leave it longer — the heat carries on travelling once it's off the pan.
5. Move the tuna straight to a board and, with your sharpest knife, slice it thinly across the grain in one clean draw per slice. Sawing tears the crust off.
6. Fan the cucumber and avocado across two plates, alternating slices, and season the avocado with a small pinch of salt — it wakes the fruit up and keeps the dish from feeling one-note.
7. Lay the tuna slices over the avocado and cucumber, slightly overlapping. Spoon the ponzu generously over and around — the lemon juice in the dressing is what cuts the richness of the tuna and avocado, so don't be shy.
8. Scatter the spring onions, red chilli and micro herbs or coriander across the top, and serve straight away while the tuna is still cool and the crust is still crisp.