Season the chicken breasts all over with 1 tablespoon olive oil, garlic powder, 1 teaspoon Italian seasoning, and a generous pinch of salt and pepper.

In a large skillet, heat the remaining 1 tablespoon olive oil over medium heat. Add the chicken and cook until golden and cooked through, about 6 minutes per side. Transfer to a plate, tent with foil, and let rest for 10 minutes before slicing.

In the same skillet, melt the butter over medium heat. Add the onion and cook, stirring, until softened, about 3 minutes. Stir in the garlic and remaining 1 teaspoon Italian seasoning, cooking until fragrant, about 1 minute.

Add the orzo pasta and stir for 2 minutes to toast lightly. Pour in the chicken broth, season with a pinch of salt and pepper, and bring to a low boil. Reduce heat to a simmer, cover, and cook for 12 minutes, until the orzo is tender.

Uncover the skillet and stir in the baby spinach, heavy cream, and Parmesan cheese. Cook, stirring, until the spinach wilts and the sauce is creamy, about 2 minutes.

Remove from heat and stir in the lemon zest and lemon juice. Taste and adjust with more lemon juice, salt, or pepper as desired.

Serve the creamy orzo topped with the sliced chicken. Garnish with lemon slices and a sprinkle of chopped parsley.