Crispy tostadas with tuna (Tostadas de atún)

1. Use only very fresh, sashimi-grade tuna that is safe to eat raw. Cut the tuna into 1 cm cubes with a sharp knife and keep in the fridge.

2. Slice the red onion into hair-thin half-moons and soak in iced water for 10 minutes to soften its bite; drain.

3. Finely chop the chipotle chili together with its adobo sauce and mix into the mayonnaise.

4. Fry the corn tortillas in hot oil for about 1 minute per side until crisp and drain on kitchen paper – now they're tostadas.

5. Right before serving, toss the tuna with the soy sauce, the juice of 1 lime and a pinch of salt.

6. Spread each tostada with chipotle mayo, top with tuna, avocado slices and onion and serve immediately with lime wedges.

Tip: Mix the tuna with the lime and soy only at the last moment – the acid quickly "cooks" the fish and dulls its colour.