Cook the pasta. Bring a large pot of water to a boil and cook the pasta according to the package until just tender. Drain, rinse briefly under cold running water for this cold salad, and drain thoroughly again. Spread loosely in a shallow bowl so it finishes cooling without sitting in trapped water.

Drain the protein ingredients. Drain the tuna and measure 400 g of fish. Rinse and drain the chickpeas well. Keep the tuna refrigerated while preparing the vegetables and dressing, using clean utensils and bowls for the ready-to-eat ingredients.

Mix the lemon dressing. Whisk Greek yogurt, lemon juice, olive oil, Dijon, salt, and pepper until smooth. Reserve about a quarter of the dressing in a small pot to refresh the portions later. Different mustard brands vary in strength, so taste before adding extra.

Fold the salad gently. When the pasta is cool, combine it with chickpeas, cucumber, tomatoes, onion, and parsley. Fold in the larger tuna flakes and about three-quarters of the dressing. Turn gently so the tuna remains visible rather than disappearing into a thick paste.

Divide into four lunches. Divide the salad evenly among four containers, making sure each gets a comparable amount of tuna and chickpeas. Add a little of the reserved dressing when serving. Refrigerate promptly rather than leaving the complete salad on the counter while preparing other meals.

Serve cold. Keep the bowls at 40°F (4°C) or colder until lunch, using cold packs for transport. Stir gently and add the reserved dressing or a teaspoon of water if the pasta has absorbed the coating. This recipe is intended for cold serving, so no reheating stage is needed.