In a 3 quart pan, combine alfredo sauce, chicken broth, red pepper, broken spaghetti and stir. Bring to a boil, reduce heat to medium-low, cover and let cook 11-15 minutes or until pasta is tender. Remove from heat.
Stir chicken breast, spinach, tomatoes, and lemon juice into the cooked pasta and sauce. Toss to combine and serve while hot with grated Parmesan cheese.