Heat the olive oil in a large soup pot over medium-high heat.
When the oil is hot and shimmering, add the diced turkey and cook for 5-10 minutes or until the turkey begins to brown.
Add the onion and half of the salt and cook, stirring occasionally, for 2-3 minutes or until the onion begins to turn translucent.
Add the celery, carrots, and remaining salt and cook, stirring occasionally for 2-3 minutes.
Add the garlic and cook for 1-2 minutes, stirring frequently.
Add the broth, bay leaf, thyme, and lemon zest. Increase the heat to high and bring to a boil.
Once the soup is boiling, reduce the heat to a simmer, cover with a lid and cook for 2 hours, stirring occasionally.
After 2 hours, increase the heat to high, return the soup to a boil, and then reduce the heat to low and stir in the spinach and lemon juice. Let the soup simmer for another 15 minutes to wilt the spinach and marry all the flavors.