This easy soup is a great way to showcase the versatility of spaghetti squash. Sweet Italian sausage pairs well with the subtle sweetness of the squash. The broth that coats the thin strands of spaghetti squash is flavorful and light.
Preheat oven to 400°F. Rub cut sides of squash with 1 tablespoon oil. Place squash, cut-sides down, on a baking sheet. Roast until tender when pierced with a fork, about 30 minutes. Using a fork, scrape the squash strands into a medium bowl.
Meanwhile, heat the remaining 1 tablespoon oil in a large skillet over medium-high heat. Add sausage and cook, using a wooden spoon to break it into small pieces, until browned, about 8 minutes. Add onion, carrots, garlic and crushed red pepper; cook, stirring often, until the onion is just translucent, about 2 minutes. Add tomatoes and broth and bring to a boil over medium-high. Reduce heat to medium-low and simmer, stirring occasionally, until the carrots and onion are almost tender, 5 to 6 minutes. Stir in kale and cook until tender, about 3 minutes. Remove from heat. Season with pepper.
To serve, place 1/2 cup squash strands in each of 6 bowls, reserving the remaining squash strands for another use. Ladle the tomato-sausage soup around the squash in the bowls.