In a large pot, heat the olive oil over medium heat. Add the diced onion and sauté until translucent, about 5 minutes.

Add the minced garlic, diced carrots, and diced celery to the pot. Cook for an additional 3-4 minutes until the vegetables start to soften.

Pour in the chicken broth and bring to a boil. Add the boneless chicken breast, dried thyme, dried basil, salt, and pepper.

Reduce the heat and let it simmer for 15-20 minutes, or until the chicken is cooked through.

Remove the chicken from the pot and shred it using two forks. Return the shredded chicken back to the pot.

Add the cheese tortellini and fresh spinach to the soup. Cook for an additional 5-7 minutes, or until the tortellini is cooked according to package instructions.

Stir in the lemon juice and adjust seasoning as needed.

Serve hot, garnished with grated Parmesan cheese if desired.