01 - Heat olive oil in a large, deep skillet or sauté pan over medium-high heat. Add chicken pieces, lightly season with salt and pepper, and cook until browned and cooked through, approximately 4 to 5 minutes. Transfer chicken to a plate and set aside.
02 - In the same pan, add chopped onion and cook until softened, about 2 minutes. Stir in minced garlic and cook for 30 seconds until fragrant.
03 - Add penne pasta, chicken broth, and halved cherry tomatoes to the pan. Bring to a boil, then reduce heat to a simmer. Cover and cook for 10 to 12 minutes, stirring occasionally, until pasta is al dente and most of the liquid has been absorbed.
04 - Return cooked chicken to the pan along with any juices. Add baby spinach and stir just until wilted, 1 to 2 minutes.
05 - Remove pan from heat. Stir in basil pesto and grated Parmesan cheese and mix until creamy and well combined.
06 - Taste and adjust seasoning with extra salt and freshly ground black pepper if needed. Serve hot, garnished with additional Parmesan as desired.