Cut the chicken breasts into 1-inch cubes and season evenly with salt, pepper, and garlic powder.
Heat a large skillet over medium-high heat and add the olive oil.
When the oil is hot, add the chicken in a single layer and cook undisturbed for 3–4 minutes, then stir and cook another 3–4 minutes until mostly cooked through; remove the chicken and set aside (it will finish cooking later).
Add the butter to the same skillet, then add the orzo and stir until the orzo is lightly browned and toasty, about 2–3 minutes.
Pour in the chicken broth, heavy cream, and lemon juice, scraping the browned bits from the bottom of the pan. Bring to a boil.
Reduce heat to low, cover, and simmer for 10–12 minutes, stirring occasionally, until the orzo is tender.
Remove the cover, stir in the Parmesan, add the cooked chicken and fresh spinach, and cook, stirring regularly, until the spinach wilts and the chicken is cooked through.
Garnish with lemon zest and serve immediately.
