Preheat a fan-forced oven to 200 degrees celsius (fan-forced). Place diced pumpkin on a lined baking tray. Drizzle with olive oil and season with salt and pepper. Bake in the oven for 30-40 minutes or until soft.
Place the halved onions into the Thermomix bowl. Chop on Speed 6, 5 seconds. Scrape down the sides of the bowl.
Add the olive oil and minced garlic and saute on 80 degrees, Speed 2, 3 minutes. Add the passata, tinned tomatoes, dried herbs, salt, pepper and sugar. Cook on Varoma, 15 minutes, Speed 2. Set aside in a seperate bowl (see notes).
Once the pumpkin has cooked, remove it from the oven and allow to cool slightly. Place the pumpkin in a clean Thermomix bowl. Add the ricotta, salt and pepper and mix on Speed 4 until smooth.
To assemble the lasagne, grease a medium-large baking dish (approximately 40cm X 25cm) and start by adding a layer of fresh lasagne sheets, followed by a layer of tomato sauce, a layer of the pumpkin/cheese mixture and then spinach leaves. Repeat until you have used all of your mixture (finish with a layer of lasagne sheets topped with the pumpkin mixture and then sprinkle over the grated cheese).
Place in an oven preheated to 180 degrees celsius (fan-forced) and cook for 25-30 minutes or until the cheese has melted and the pasta is cooked through.