Preheat the oven to 425 degrees Fahrenheit. Cut the butternut squash in half length-wise. Scoop out the guts and seeds and discard. Sprinkle with salt and pepper.
Roast the butternut squash open-faced on a parchment-lined baking sheet with the peeled and roughly chopped onions at 425 for 40 minutes or until the squash is fork tender.
While squash is roasting, make the vegan cheese sauce. Add the plant milk, plant-based cheeses, and spices into a pot and bring the mixture to a boil until all of the cheese is melted.
Also while the squash is cooking, bring large pot of water to a boil. Cook the pasta 1-2 minutes less than al dente per package instructions.
When the squash is fork-tender, remove it from oven, and let it cool slightly before handling. Reduce the oven temperature to 350 degrees.
Scoop out 2 cups of cooked butternut squash and add it to the cheese sauce with the onions.
Use immersion blender to blend the cheese sauce until smooth. Some chunks of squash are ok if you prefer.
Add the almost al dente pasta to a medium baking dish and cover with the butternut squash cheese sauce. Stir until all noodles are evenly coated.
Mix the breadcrumbs and oil together in a small bowl, then sprinkle it on top of the noodles with more plant-based parmesan cheese.
Place the baking dish back in the oven at 350 degrees Fahrenheit for 10-15 minutes or until breadcrumbs are golden brown. Optional to broil for the final 5 minutes for a crispier top.
Serve and enjoy!