Remove any tough outer leaves from the fennel and reserve the feathery green fronds for garnish. Chop the fennel, onion, and peppers into a very fine quarter-inch dice.

Halve the cucumber and scoop out the seeds with a spoon before dicing it to match the other vegetables, then toss everything in a bowl with cilantro, salt, and nigella seeds.

Finely mince the mint and green chile and mix them with the yogurt, lemon juice, and sugar. Taste and adjust the seasoning until you have a perfect balance of citrus and heat.

Pour the creamy dressing over the vegetables just before serving and mix well. Finish the dish by scattering the reserved fennel fronds and an extra pinch of nigella seeds on top.