Cook 150g spaghetti according to pack instructions. Place the spinach into a large colander, then drain the pasta slowly over the top, giving the leaves a chance to wilt. Return both to the spaghetti pan with the prawns and their dressing, then toss well, until the prawns are hot.
Meanwhile, scrub the lime, add the finely grated zest (keeping a little to garnish) and ½ the juice to the pan. Season to taste. Serve in wide bowls with the reserved zest on top, and lime wedges on the side for squeezing over.
