Roasted Tuna with Herb Butter

Beat the softened butter in a bowl until smooth. Fold in the tarragon, chives, parsley, Dijon mustard, minced shallot, lemon zest, lemon juice, and fleur de sel until evenly combined. Spoon onto a sheet of cling film, roll into a log approximately 4cm in diameter, twist the ends tight, and place in the refrigerator.

Refrigerate the butter log for at least 30 minutes until fully set.

Season the tuna steaks generously on all sides with fleur de sel and cracked black pepper.

Heat the oil in a heavy-based cast-iron or stainless-steel skillet over the highest heat until the oil begins to smoke and shimmer — approximately 2 minutes.

Place the tuna steaks in the pan and sear undisturbed for 90 seconds, until a deep mahogany crust has formed on the underside and the colour has crept 4–5mm up the sides of the steak.

Flip the steaks once and sear for a further 60 seconds for a rare-to-medium-rare centre. Use a meat thermometer to confirm an internal temperature of 46–50°C for rare or 63°C for fully cooked through — remove at your preferred doneness, either is safe to eat.

Transfer the tuna immediately to a warm plate and rest uncovered for 2 minutes.

Slice the chilled butter log into rounds approximately 1cm thick. Place two rounds on each steak while still hot and allow them to melt into the crust.

Serve at once with watercress or rocket alongside and lemon wedges for squeezing.