Place chicken, onion, enchilada sauce, salsa, spices, and broth in the slow cooker. Season with salt and pepper.
Cook on low 6–7 hours, or high 3–4 hours, until chicken shreds easily.
Shred chicken with two forks in the cooker and stir to coat in sauce.
Spoon 1/4 cup filling into each tortilla, roll snugly, and place seam-side down in a greased baking dish.
Pour any extra sauce over the rolled enchiladas and sprinkle with cheese.
Broil 3–5 minutes until cheese melts and bubbles, then garnish with cilantro and serve.