Use two medium bowls, add chicken to one and bell peppers, onion, and jalapeno to the other. Combine in a small bowl, olive oil, black pepper, cumin, chili powder, cayenne, salt, and cilantro. Divide oil mixture evenly over chicken and bell pepper mixture, toss both to combine.
Heat a large skillet to medium-high heat, add chicken, and sear on both sides. Remove chicken and place on a plate while cooking peppers. Reduce heat to medium, add bell pepper mixture to the same skillet and cook until tender, about 8 to10 minutes. Return chicken to skillet with peppers, add chicken broth and cook until chicken is done and broth has cooked down.
Oven Method: Preheat the oven to 300 degrees. Wrap tortillas that are stacked on top of each other, in a damp dishtowel and place in a covered casserole dish. Warm for 15 to 20 minutes while chicken cooks.
Microwave Method: A microwave can be used as an alternative. Stack tortillas, with a paper towel in between each one, cover with a damp dishtowel and warm for 1 minute. Serve immediately.
Evenly divide fajitas between 6 tortillas, add Greek yogurt and cheddar cheese.