Pat the chicken dry and toss it with the Italian seasoning, 1/2 teaspoon kosher salt, and black pepper.

Heat 1 tablespoon olive oil in a large, deep skillet or Dutch oven over medium-high heat. Brown the chicken for 3–4 minutes per side until well colored, then transfer it to a plate; it does not need to be fully cooked yet.

Add the remaining olive oil and cook the diced onion for 3–4 minutes until softened. Stir in the garlic and tomato paste and cook for about 30 seconds.

Stir in the dry orzo and toast it for 1–2 minutes, allowing the pasta to pick up the savory flavors in the pan.

Add the diced tomatoes, chicken broth, and remaining 1/2 teaspoon salt. Stir well while scraping up the browned bits from the bottom of the pan.

Return the chicken and any accumulated juices to the skillet. Bring the mixture to a simmer, cover, and cook for 10–12 minutes, stirring once or twice, until the orzo is tender and the chicken reaches 165°F/74°C internally.

Stir in the baby spinach until wilted, then mix in the Parmesan and lemon juice. If the orzo is too thick, loosen it with a splash of hot broth or water.

Let the skillet rest for 3–5 minutes, then garnish with fresh parsley or basil and additional Parmesan before serving.