Begin by searing the chicken breasts in a hot skillet for about 2-3 minutes per side until golden; then, transfer to a slow cooker.
Add diced onion and minced garlic to the skillet; cook until fragrant and translucent, about 3 minutes. Pour in tomato sauce, cumin, paprika, and broth, stirring to combine.
Pour the sauce mixture over the chicken in the slow cooker and cook on low for 3-4 hours until the chicken is tender and shreds easily.
Once cooked, remove the chicken and shred it using two forks, then return it to the sauce in the slow cooker, mixing well.
While the chicken is cooking, prepare the peppers by cutting off the tops and scooping out the seeds and membranes carefully over the sink.
Stuff each pepper generously with the shredded chicken mixture, then top with shredded cheese so it melts into the filling.
Place the stuffed peppers upright in the slow cooker, optionally cover with foil, and cook on high for another 30 minutes until the cheese is bubbly and slightly golden.
Remove the peppers carefully from the slow cooker, letting any excess sauce drip off, and serve hot with a side salad or your favorite sides.
