Chop fresh spinach and set aside.
Whisk eggs, salt, pepper and parmesan cheese together and set aside.
Bring chicken broth, lemon juice, lemon zest and garlic to a boil; add chopped spinach and mix to incorporate.
When broth is boiling, add eggs in a steady, slow stream, whisking broth rapidly to break eggs up as they are incorporated into the broth.
When all eggs are blended with broth, reduce heat to a simmer and cook for an additional 2-3 minutes.
Serve immediately; garnish with additional parmesan cheese if desired.