Slice the bell peppers into strips about 1/4-inch thick, keeping the slices uniform for even cooking and vibrant color.
Peel and slice the onion into thick rings or strips, which will soften beautifully and caramelize during cooking.
Pat the chicken breasts dry with paper towels, then cut into 2-inch strips or chunks, making them easy to cook and serve.
In a small bowl, toss the chicken pieces with the fajita seasoning until evenly coated, ensuring every piece is flavorful.
Heat a tablespoon of olive oil in a skillet over medium heat, then quickly brown the chicken for 3-4 minutes until just starting to turn golden and develop a little crust.
Transfer the browned chicken to the slow cooker, then add the sliced peppers and onions on top, along with a squeeze of fresh lime juice.
Pour in about half a cup of chicken broth or water, then gently stir everything together to combine the flavors without breaking the peppers or onions.
Cover the slow cooker with its lid and cook on low for 4 to 6 hours, until the chicken is tender and easily shredded, and the peppers are soft and smoky smelling.
Check the fajitas at around 4 hours; the chicken should shred easily with a fork and the peppers should be caramelized and fragrant.
Turn off the slow cooker and let the fajitas rest for 5 minutes; this helps the juices settle and intensifies the flavors.
Serve the fajitas hot with warm tortillas, garnished with fresh cilantro or extra lime if desired, for a colorful and flavorful meal.
