"I searched high and low for a great recipe for slow cooker fajitas before I came up with this. The best part for me is that I don't have to defrost the meat before I throw it in there. Also, this makes a very large batch, so it's good for big families or a crowd of guests."
Combine chicken breasts, tomatoes, salsa, chili powder, salt, paprika, sugar, onion powder, garlic powder, bouillon granules, cumin, cayenne pepper, and red pepper flakes in a slow cooker.
Cover and cook on Low until chicken is tender, about 5 hours. Transfer chicken to a cutting board; shred using 2 forks. Return to the slow cooker. Add onions, red bell pepper, yellow bell pepper, green bell pepper, and cornstarch.
Cook on Low until peppers soften, 1 1/2 to 2 hours. Serve chicken and peppers with tortillas, Cheddar Jack cheese, and sour cream.