- Preheat the oven to 400°F and grease a 9-inch cake or pie pan. Place the squash, cut side up, on a large baking sheet, and bake for about 50 minutes, or until tender. Set aside to cool slightly.
- In a large sauté pan, heat the olive oil over medium heat. Add the onion and sauté for 3 minutes. Add the asparagus and garlic and sauté for about 5 minutes, or until the asparagus is soft and bright green. Remove from the heat and set aside to cool.
- In a large bowl, whisk together the eggs, milk, cheese, salt, and pepper, then add the cooled onion-asparagus mixture and stir to combine.
- Using a fork, scrape the strands from the spaghetti squash and transfer to the bottom and sides of the greased cake pan, creating an even crust. Press paper towels onto the crust to remove any excess moisture (or you can wring the squash out ahead of time). Pour the egg mixture onto the “crust” and bake for 40 minutes, or until the pie is firm and not wiggly.