Heat the oil in a large saucepan, add the onion and cook over a medium-high heat for 10 mins, adding a splash of water if the onions stick. Add the okra, garlic and allspice, toss to coat the okra in spices, then add the passata. Pour in 100ml of water, cover and simmer for 40 mins or until the okra is tender.
Pour 350ml boiling water over the couscous, cover and leave to stand for 10 mins, then season and stir with a fork to break up any clumps.
Stir the lemon juice into the okra, then serve on top of the couscous with feta and parsley scattered over, or yogurt spooned on top.