Place the couscous, lemon and herb in a glass or stainless steel bowl. Pour over 1½ cups boiling water and cover for 5-10 minutes. Remove the lemon and herb sprig and fluff up with a fork.
Step 2
Flake the tuna and toss gently with the onion, zucchini, chilli, herbs and lemon zest. Dress the tuna salad with the lemon juice, olive oil and season well. Serve with a sprinkle of sesame seeds.