Heat oil in large saucepan over medium-high heat, add onion and cook for about 3 minutes.
Add celery, carrot and broccoli to pan and saut for about 5 minutes.
Add in all seasonings and cook additional 1 minute.
Add water, tomato paste, chickpeas and lentils, bring to a boil. Cover, reduce heat to low and simmer for 20 minutes.Meanwhile, cook couscous in separate pan according to package directions.
Add cilantro and lemon juice to stew and serve over warm couscous.