Place the trout in a dish, skin side up. Sprinkle ½ tbsp Cajun seasoning over each fillet and gently rub it in. Set the trout to one side.
Pour the quinoa into a sieve. Rinse it well under cold water for 1-2 mins (see our tip). Tip into a pan. Add 150 ml boiling water. Cover. Gently simmer for 15 mins till cooked and the water has been absorbed.
Trim and peel all the carrots. Coarsely grate them. Chuck them in a bowl. Trim the spring onions. Finely slice them. Add them to the carrots. Shred the lettuce and add that too.
Finely grate and juice the lime. Measure out 1 tbsp of the vinegar and add it to the lime juice. Measure out 1 tsp of the honey (keep the rest for the Grilled Chicken with Blackcurrant Sauce).
Add a pinch of salt to the lime dressing. Whisk to combine all the ingredients. Taste and add more salt if you think it needs it. Add to the slaw. Toss to mix.
Heat your grill to high. Line the grill pan with foil. Place the trout on a rack in the pan, skin side up. Cook for 10-12 mins till the trout skin is golden and crisp and the trout flakes easily when pressed with a fork.
Fluff up the quinoa with a fork. Serve the trout with the quinoa and summer slaw.