• 1 red onion, very finely sliced, ideally on a mandoline
• 3 tablespoons lime juice, plus extra to taste
• 1 tablespoon coriander seeds
• ½ teaspoon sea salt flakes
• freshly ground black pepper
• ¼ teaspoon cayenne pepper
• ½ teaspoon ground cumin
• 500 g (1 lb 2 oz) watermelon, cut into bite-sized pieces
• 200 g (7 oz) peeled and diced cucumber
• 3 tablespoons chopped coriander (cilantro)

Put the onion in a small bowl and pour over the lime juice. Set aside.

Toast the coriander seeds in a dry frying pan until fragrant. Transfer to a mortar and lightly crush. Mix with the salt, black pepper, cayenne pepper and cumin.

Gently combine the watermelon, cucumber, marinated onion and chopped coriander in a large bowl. Sprinkle over the spice mix and toss. Taste for seasoning and add more lime juice, if you like.