Preheat your oven to 375°F (190°C) and lightly grease a 9x13 inch baking dish.

In a medium bowl, combine the shredded chicken, half of the chopped onion, and half of the shredded cheese.

Warm the tortillas briefly in the microwave or a dry skillet to make them pliable.

Dip each tortilla in the enchilada sauce to coat it lightly.

Place a portion of the chicken mixture down the center of each tortilla, then roll it up tightly and place seam-side down in the prepared baking dish.

Pour the remaining enchilada sauce over the rolled enchiladas, ensuring they are well covered.

Sprinkle the remaining shredded cheese and chopped onion over the top.

Bake for 20-25 minutes, or until the cheese is melted and bubbly and the enchiladas are heated through.

Let the enchiladas rest for a few minutes before serving. Garnish with your favorite toppings like sour cream, cilantro, or jalapeños.