Preheat the oven to gas 6, 200°C, fan 180°C.
Rub a little olive oil over the pepper, place on an oven tray and roast until charred. Place into a freezer bag and leave until cooled.
Once cooled tip the pepper into a bowl, peel of the skin, chop into strips then pour the juices into a measuring jug through a sieve and make up to 100ml with boiling water.
Add the couscous and lemon zest, cover with clingfilm and leave until required.
In a large mixing bowl add the peeled chopped cucumber, sliced red onion, chopped tomatoes, roasted pepper strips and black olives. Drizzle the olive oil and lemon juice over, season with salt and black pepper and mix well.
Break the cooled couscous up with a fork before adding the chopped parsley to it and mixing. Gently toss the salad with the couscous, then divide on to plates. Finally, scatter over the tuna and feta, garnish with fresh basil leaves and serve.
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