Preheat oven to 170C (fan 150C) /325F.
Wash and dry the zucchini, then cut in half through the stem and bottom end.
With a melon melon baller or spoon, scoop out the seeds and flesh from each half, leaving about a half-inch shell and reserving the flesh.
Bring water or stock to a boil. Pour the couscous in a bowl. Add the hot stock and stir using a fork.
Cover and rest for 6-8min, until the liquid is absorbed.
Once the couscous is cooked and tender, fluff it a little with a fork, breaking up any lumps.
In the meantime, heat the olive oil in a frying-pan over medium heat.
Add the tomato paste and stir for 2 min, then add the onion and stir all ingredients.
Take the pan off the heat , season with salt and pepper to taste and mix well with the cous cous.
Fold in all the remaining ingredients, then add the reserved zucchini flesh.
Fill each zucchini with the cous cous salad.
Place zucchini and their tops on an oven tray covered with parchment paper.
Brush with olive oil and bake in the oven for 20 min.
Serve hot from the oven or at room temperature. Enjoy!