Trim the fat from the lamb kidney and dice it.

Soak the diced kidney in plenty of vinegar water for 30 minutes; this step noticeably cuts the sharp smell.

Drain the kidney and rinse it with clean water, put it in a pot with the onion, cover with water, and bring to a boil, skimming off the first foam.

Add the cumin, chilli flakes and salt, cover, and simmer on low heat for 90 minutes until the kidney is tender.

Whisk the eggs with the lemon juice, then temper them by slowly stirring in a ladle of hot broth, and add the mixture back to the soup, simmering for 15 more minutes while stirring.