Season the boneless, skinless chicken breasts with cumin and chili powder evenly on both sides. In a large skillet, heat vegetable oil over medium heat, adding the chicken. Cook for about 8 minutes, or until the chicken reaches an internal temperature of 165°F and is no longer pink. Remove from the skillet, let it rest for a few minutes, and then shred the chicken using two forks.

In the same skillet, add the diced onions to the leftover chicken fat and sauté over medium heat. Cook for 5-7 minutes, stirring occasionally, until the onions become golden and caramelized, bringing out their sweetness. Set the caramelized onions aside on a plate, allowing them to cool slightly while you prepare the enchilada sauce.

Lower the heat and pour the green enchilada sauce into the skillet, scraping up any delicious bits left from the chicken and onions. Gently heat the sauce on low for about 5 minutes, allowing it to warm through and blend the flavors. It should simmer softly while you move on to preparing the tortillas.

In a separate dry skillet over medium-high heat, warm the corn tortillas one at a time for about 30 seconds on each side. This helps soften them and adds flavor; they should be slightly pliable but not crispy. Once warmed, stack them in a clean towel to keep them warm while you assemble your Chicken Enchiladas.

Take a warm tortilla, dip it in the enchilada sauce, coating both sides lightly. Place the tortilla on a clean surface and fill it with shredded chicken, a spoonful of caramelized onions, and some grated cheese. Roll the tortilla tightly and place it seam-side down in a greased casserole dish. Repeat this process for each tortilla until all ingredients are used.

Once all enchiladas are assembled in the casserole dish, pour any remaining enchilada sauce over them, ensuring they are well covered. Sprinkle the top with the remaining cheese and a dash of chili powder for garnish. Preheat your oven to 350°F and bake for 30 minutes, or until the cheese is bubbly and slightly golden.

After baking, remove the Chicken Enchiladas from the oven and let sit for 15-20 minutes. This resting period allows the flavors to meld and makes serving easier. Garnish them with diced tomatoes, a dollop of sour cream, and chopped cilantro for a fresh finish before serving warm to your family.