Optional: 1/4 cup Mexican blend cheese, more for topping
If you don't already have spaghetti squash cooked, start by doing that: Preheat oven to 375ºF and line a baking sheet with foil or parchment paper. Cut spaghetti squash in half, lengthwise. Scoop out seeds. Brush inside with oil. Place facedown on baking sheet and add 1 tablespoon or so of water to the baking sheet. Bake for 45-50 minutes, or until you can pierce with a fork. Once done, scrape out squash into spaghetti stands and set aside. See this article for more info on cooking spaghetti squash.
While cooking, sauté the veggies: Over medium heat, add 1 tablespoon oil and sauté onions and peppers for 5-8 minutes until soft. Add in spinach and mix to wilt. Set aside.
Make the Enchilada Sauce: In a small saucepan over medium-high heat, heat the oil. Add the arrowroot flour and stir together over the heat constantly for 1 minute. Stir in the chili powder, garlic powder, onion powder, cumin, and salt. Then add the tomato sauce and gradually add the chicken broth, whisking to remove any clumps. Reduce the heat and let simmer for 10 minutes or until the sauce thickens. Taste and adjust any spice as desired.
Assemble and Bake: Preheat oven to 350ºF. In a large bowl combine cooked spaghetti squash, shredded chicken, sautéed veggies, refried beans, enchilada sauce, and optional cheese. Spread evenly into a greased baking dish and top with additional optional cheese. Bake for 20-30 minutes until cheese is bubbly. Garnish and serve.
Omit cheese and beans for dairy-free, paleo, and Whole30-compliant!