Prepare the slow cooker with cooking spray or olive oil. In the bottom of the slow cooker add in the diced tomatoes, chili powder, cumin, minced garlic, cinnamon, onion powder, salt, and pepper. Stir to combine.
Add the chicken to the slow cooker and mix together. Cook on low for 3-4 hours or high for 2 hours. Add in the bell peppers and onions. Cook on high for another hour.
Remove the chicken and shred with two forks. Add the shredded chicken back into the slow cooker. Add fresh squeezed juice of one lime and combine.
Serve the fajita mixture on warm tortillas with desired toppings!
Notes
Substitutions: You can use green peppers or sweet onion instead. You can also use your favorite fajita or taco mix if you prefer!