Pour 1/2 cup of the diced tomatoes in the bottom of a 5-6 quart slow cooker. Add the remaining ingredients in this order: chicken breasts, onion, bell pepper, garlic, black pepper, salt, remaining diced tomatoes, balsamic vinegar, basil, oregano, and red pepper flakes. Cover and cook on high 4-5 hours or low 6-7 hours.
If desired, serve chicken over a bed of whole wheat spaghetti, brown rice, or quinoa.
Sprinkle parmesan cheese on top of chicken before serving.