Preheat your oven to 375°F (190°C).

In a skillet over medium heat, add 1 tablespoon of olive oil. Once hot, add the diced onions and sauté for about 3-5 minutes, until they turn translucent and fragrant.

In a large mixing bowl, combine the shredded chicken, sautéed onions, 1/3 cup of enchilada sauce, and half the cheese. Stir until well incorporated.

Place a tortilla on a flat surface. Add about 1/4 cup of the chicken mixture in the center and roll the tortilla tightly to enclose the filling. Place the rolled enchilada seam-side down in a greased baking dish. Repeat with remaining tortillas.

Pour the remaining enchilada sauce evenly over the top and sprinkle with the remaining shredded cheese.

Place the baking dish in the preheated oven and bake for about 20 minutes, or until the cheese is bubbly and golden brown.

Once out of the oven, let the enchiladas cool for a few minutes before serving with fresh toppings like cilantro or sour cream.