Preheat the oven to 200°C conventional / 180°C fan-forced.
Bring a large saucepan of well-salted water to the boil. Cook the pasta for about 2 minutes less than the packet instructions. Drain and set aside.
Meanwhile, heat the olive oil in a large frying pan over medium heat. Add the onion and cook gently for about 5 minutes, until softened.
Add the garlic and crushed fennel seeds and cook for another minute, until fragrant.
Stir in the tomato paste and cook for 1–2 minutes before adding the passata. Season with salt and pepper and simmer gently for about 10 minutes.
While the sauce is cooking, combine the ricotta, lemon zest and Parmesan in a small bowl. Season well with salt and pepper.
Add the drained pasta and tuna to the tomato sauce. Gently fold everything together, keeping some of the tuna in lovely larger flakes.
Spoon half the pasta mixture into a baking dish. Dollop over half of the lemony ricotta. Add the remaining pasta and spoon over the rest of the ricotta, nestling it into the pasta rather than completely mixing it through.
Scatter over the mozzarella and Parmesan.
Bake for 20–25 minutes, until bubbling around the edges and golden on top.
Allow to stand for 5 minutes before serving.