Heat the oven to 160°C/Gas 3. Place the couscous in a large heatproof bowl and pour the boiling water on top. Add the olive oil and diced butter, and toss them through with a fork. Cover and place in the oven for 15 minutes.
Meanwhile, finely slice the onions. Heat the oil in a pan and fry the onions until soft. Add the garlic, tomatoes, sugar, salt, pepper, saffron, paprika, ginger and