2.Combine onion, kumara and oil in a large baking dish; season. Roast, uncovered, stirring once, for 25 minutes or until vegetables are tender.
3.Meanwhile, cook pasta in a large saucepan of boiling water until just tender; drain.
4.Combine pasta in a large bowl with spinach, ricotta, garlic, cream and tomatoes; season.
5.Spread kumara mixture over the base of a 3-litre (12-cup) baking dish. Top with pasta mixture; sprinkle with nuts and parmesan. Bake, covered, for 5 minutes. Uncover; bake for a further 5 minutes or until browned.
The kumara mixture can be roasted and the pasta cooked several hours ahead. Assemble close to serving. From cold, bake, covered, at 200°C/400°F for 30 minutes or until heated through then uncover and bake for a further 10 minutes or until browned.