1. Place the cashews in a heatproof bowl, cover them with boiling water, and let soak for at least 30 minutes before draining.
2. While the cashews are soaking, heat the olive oil in a large soup pot over medium-high heat. Add the onions and sausage, cooking until the meat is browned and the onions are softened, about 6 to 8 minutes, breaking the sausage apart as it cooks.
3. While this mixture cooks, blend the drained cashews with nutritional yeast and 2 cups of broth in a high-speed blender until completely smooth and silky, then set aside.
4. Reduce the heat to medium and stir in the garlic, Italian seasoning, tomato paste, salt, and pepper. Cook for 1 to 2 minutes until fragrant and the tomato paste deepens in color. Stir in the diced tomatoes and the remaining 6 cups of broth, bring the soup to a gentle boil, then lower the heat and simmer for 10 to 15 minutes, stirring occasionally, until the flavors meld and the vegetables are tender.
5. Stir in the cashew cream and baby spinach, allowing the soup to simmer for another 2 to 3 minutes until the spinach wilts. Taste and adjust the seasoning as needed.
6. Just before serving, stir the zucchini ribbons directly into the pot, or place them into individual bowls and pour the hot soup over them to gently soften.
7. Ladle into bowls and top with fresh basil or parsley, parmesan or dairy-free parmesan, and pine nuts if desired.