Set out an 8x8 deep casserole dish and preheat the oven to 350°F.
Chop onions and garlic in small pieces. Sauté them in a heated pan with olive oil until the onions are translucent. Separate them into 3 parts, one for each layer.
For the pumpkin layer, use canned pumpkin or cook the fresh pumpkin in a steamer or boiling water. Set the cooked pumpkin in a medium bowl with 1 part of the sautéed onions and blend until you get a smooth puree. Add salt and pepper to taste.
For the spinach-ricotta layer: Set the previously soaked cashews in a food processor with nutritional yeast and non-dairy milk. Mix this “ricotta” with the spinach (already defrosted) in a medium bowl. Add another portion of the sautéed onions. Stir until combined. Add salt and pepper to taste.
For the beetroot layer: Set the beetroot slices in a medium bowl with the last part of the sautéed onions and blend until you get a smooth puree. Add salt and pepper to taste.
To make the bechamel sauce: Add the non-dairy milk, cornflower, olive oil, and salt/pepper to a small pot on high heat and whisk for 5-10 minutes. Is normal to have some lumps, just keep on whisking and add more milk if needed being sure to not let it burn or stick. Set aside once thickened.
Using a deep 8x8 inch casserole dish, coat the bottom of the dish with tomato sauce, then add a layer of noodles. Then set the layers as desired, alternating filling and noodles. The final layer of noodles should be completely covered with bechamel sauce. If you’re using a larger dish your layers will be thinner.
Bake in the oven for 30 minutes or until the top is golden brown. Serve immediately or store leftovers in an airtight container in the fridge for up to 4 days.