1. Preheat the oven to gas 7, 220°C, fan 200°C and line a large baking tray with nonstick paper. Drizzle the courgette halves with ½ tbsp oil, season and bake for 15 mins.
2. Meanwhile, mix the rice, tuna, olives, capers and egg in a bowl and set aside.
Mix the breadcrumbs, parsley, garlic and Parmesan in a separate bowl. Add the remaining ½ tbsp oil; toss to coat.
3. Fill the courgettes with the tuna mix and top with the herby breadcrumbs.
4. Bake for 15-20 mins until the courgettes are soft and the crumbs are crisp.
5. Divide the tomatoes between 4 plates, top with the onion and some parsley, then season. Serve with the courgettes.