Place chicken breasts, chili powder, cumin, coriander, and salt in a pot over medium-low heat. Add enough water to cover. Simmer chicken until no longer pink in the center, about 30 minutes. Remove chicken from the broth and cool until easily handled, about 10 minutes.

While chicken is cooling, continue boiling broth until reduced to about 3 cups.

Heat olive oil in a skillet over medium heat. Saute green bell pepper, onion, and garlic until tender, about 5 minutes. Stir in tomatoes and cook until heated through.

Add 1/2 of the vegetable mixture to the chicken broth. Stir in sour cream and simmer, stirring often, until sauce is the consistency of a thin gravy, about 15 minutes.

Preheat the oven to 350 degrees F (175 degrees C). Coat a 9x13-inch baking dish with cooking spray.

Shred chicken with two forks and stir into the remaining vegetable mixture. Place 1/6 of the chicken mixture down the center of each tortilla. Roll up tortillas and place seam-side down in the prepared baking dish. Pour sour cream sauce evenly over tortillas. Cover baking dish with foil.

Bake in the preheated oven until heated through, about 30 minutes. Uncover and sprinkle Cheddar cheese over the top. Continue baking until cheese is melted and sauce is bubbly, about 10 minutes. Let stand for 5 minutes before serving.