Heat 2 tablespoons olive oil in a large pot over medium heat.
Add 1 diced large onion, 2 chopped celery stalks, and 2 peeled and diced carrots. Cook for 5–7 minutes until the vegetables are softened.
Add 3 minced garlic cloves and cook for 1 minute until fragrant.
Stir in 4 cups chopped leftover turkey and 1 medium head cauliflower cut into small florets.
Pour in 6 cups turkey or chicken broth and add 1 can (14.5 ounces) diced tomatoes, 2 teaspoons dried thyme, 1 teaspoon dried rosemary, 1 teaspoon salt, 1 teaspoon smoked paprika, ¼ teaspoon black pepper, and 1 bay leaf.
Bring the soup to a boil.
Reduce the heat and simmer for 20–25 minutes, or until the cauliflower is tender.
Add 2 cups baby spinach and cook for 2–3 minutes until wilted.
Remove the soup from the heat and stir in 2 tablespoons fresh lemon juice.
Remove and discard the bay leaf.
Garnish with chopped fresh parsley if desired before serving.
Notes
For a thicker soup, you can puree 1-2 cups of the soup and stir it back into the pot.If you prefer cauliflower rice instead of florets, add it in the last 5 minutes of cooking to prevent it from becoming too mushy.I included chicken broth in the recipe but you can use turkey broth as well if you have any available.Refrigerate any leftovers in an airtight container for up to 5 days.