Cut chicken into 1-inch pieces, and sprinkle with salt and pepper.
Heat oil in a large nonstick skillet over medium-high heat; add chicken, onion, and garlic. Sauté 5 minutes, stirring frequently. Stir in broth and tomatoes. Bring to a boil; reduce heat and cook 5 minutes, stirring occasionally. Add spinach, basil, and butter; cook 2 minutes.
Toss chicken mixture with pasta, and top with cheese.