Preheat oven to 425. Place rack in upper third of oven.
Place peeled and cut butternut squash in large bowl, drizzle with enough olive oil that all squash is lightly coated. Sprinkle with sea salt and freshly ground pepper, toss. Place seasoned squash on rimmed cookie sheet (preferably covered with parchment paper) and roast for 45-50 minutes, or until cooked to your liking. I like mine with browned edges. While butternut roasts start onions...
To caramelize onions: Drizzle 1 Tablespoon olive oil into pan on medium heat. Add sliced onion. Sauté, stirring occasionally until well caramelized (20 -25 minutes) then sprinkle with a little sea salt and pepper. Take off heat and set aside.
Place large pot of water to boil and cook pasta to package instructions. While pasta water heats, grate cheese, and whisk together 2 tablespoons olive oil and minced garlic. Set aside.
Place fresh spinach into the bottom of a large bowl. When pasta is ready, strain in a colander (do not rinse) pour hot pasta over spinach and allow the pasta to steam the spinach for a minute. Drizzle the pasta with olive oil and garlic mixture, toss. Add caramelized onions, and roasted squash, toss again.
Add cheese, pine nuts and sprinkle with sea salt to taste, toss and serve.