Add the sweetcorn, chopped jalapeño (reserve extra slices for garnish), lime juice, olive oil, salt and pepper. Mix gently until combined. Taste and adjust seasoning — add more lime or salt if needed. Set aside in the refrigerator while you prepare the other components.

Charred Spring Onion Mayo

Heat a heavy skillet or grill pan over medium-high heat until very hot. Trim root ends from the reserved spring onion whites and keep the long greens for garnish. Lightly coat the spring onions with a little oil.

Place the spring onions on the hot pan and char until blackened in spots and softened, about 2–3 minutes per side. Remove and let cool slightly.

Finely chop 3–4 of the charred whites (reserve a couple for garnish if desired). In a small bowl, combine the chopped charred spring onion, mayonnaise, Greek yogurt (if using), smoked paprika, salt and black pepper. Stir until smooth. Taste and adjust seasoning. Refrigerate until needed.

Rainbow Slaw

In a large bowl combine the shredded red and green cabbage, grated carrot, sliced red bell pepper and chopped cilantro.

Whisk together the rice vinegar, olive oil, honey (or sugar) and salt. Pour the dressing over the slaw and toss to combine. Let sit for 5–10 minutes to soften slightly and allow flavors to meld. Refrigerate until assembly.

Crispy Onions & Garnish

If using store-bought crispy onions, separate into small clusters for easy topping. If you want to make quick homemade crispy onions: thinly slice 1 small onion, dust lightly with flour and a pinch of salt, and fry in 2–3 tbs oil over medium-high heat until golden and crisp; drain on paper towels.

Thinly slice reserved spring onion greens and extra jalapeño for garnish. Quarter the limes for serving.

To Serve

Toast the buns or warm tortillas: spread butter or brush oil on cut sides and toast in a skillet or grill until golden, about 1–2 minutes per side.

Spread a generous layer (about 1 tbs) of the charred spring onion mayo on the bottom half of each bun or on the tortilla.

Spoon a quarter of the tuna and sweetcorn mixture onto each bun (about 3.5 oz / 100 g tuna mixture per serving). Top with a handful of rainbow slaw.

Scatter crispy onions over the slaw, add a few slices of jalapeño if you like heat, and sprinkle with chopped chives or reserved spring onion greens.

Finish with a squeeze of lime, place the top bun, and serve immediately.