Pour the boiling water into a bowl then stir in stock cube until dissolved. Add couscous, cover and let soak for 5 minutes until water is absorbed.
Meanwhile heat 1 tablespoon olive oil in a frying pan and fry onion until soft and lightly browned. Add carrots and red pepper and cook and stir until soft, stirring often. Add sweetcorn, stir and take off the heat.
Fluff couscous with a fork, transfer to a large salad bowl and mix with the vegetables and 3 tablespoons olive oil. Pour in lime and orange juice. Season with salt and pepper to taste and stir in dill. Serve warm or chilled.