Heat the olive oil in a Dutch oven over medium-high heat and cook the onion, carrots and celery for 5 minutes.

Add the chicken and salt and cook for 3 minutes, stirring until the outside loses its pink color.

Pour in the broth, bring it to a boil and stir in the orzo.

Simmer for 9 to 11 minutes, stirring often, until the orzo is tender and every chicken piece reaches 165°F.

Stir in the lemon zest, lemon juice and spinach and cook for 1 minute until the leaves wilt.