Put the quinoa in a sieve and rinse well, then put in a medium saucepan and add the stock. Bring to the boil, then reduce the heat to medium and simmer for 10–12 minutes, uncovered, until the germ separates and most of the stock has been absorbed. Drain well, then leave to cool.
Meanwhile, cook the broad beans in a saucepan of boiling water for 1–2 minutes. Drain, then put in a bowl of cold water and leave the beans to cool slightly. Drain again, then slip off and discard the skins and set the beans aside.
Heat a frying pan until hot, add the cumin seeds and dry-fry over a medium heat until lightly brown, then remove from the pan and set aside. When cooled, lightly crush the seeds.
Remove the peel and pith from the lemons and cut each one into segments, discarding any seeds, then put into a large bowl. Squeeze any remaining juices into the bowl.
Peel, stone and thickly slice the avocados, add to the bowl and toss in the lemon juice. Add the drained quinoa, broad beans, toasted cumin seeds and the remaining ingredients, then season. Toss to mix well and serve.