Lightly spray a medium saucepan with oil, add the onion, garlic, carrot and celery and cook gently for about 15 minutes or until soft. (Add a few drops of water if the pan gets too dry.) Increase the heat and stir in the wine. Add the tomatoes, reduce to a simmer and cook for 10 minutes until the sauce is smooth and thick.
Add the prawns and simmer for 3—4 minutes or until the prawns are just cooked. Stir in half the lemon rind.
Meanwhile, steam the potatoes, then toss them in the remaining lemon rind, pepper and oil. Serve them with the prawns, garnished with rocket.