Char the corn tortillas over medium heat until bubbly and slightly browned for about 30 seconds per side.

Season boneless skinless chicken breasts with cumin and chili powder, then heat vegetable oil in a skillet and cook the chicken for 4-5 minutes per side until golden and cooked through.

Sauté diced onions in the same skillet over medium heat until golden, then mix in the green enchilada sauce to warm gently.

In a baking dish, pour 2 cups of the warm sauce mixture at the bottom. Dip each charred tortilla in the remaining sauce, fill with chicken, cheese, and onions, then roll tightly.

Top the enchiladas with any leftover sauce and a layer of grated cheese. Bake at 350°F (175°C) for about 30 minutes until bubbly.

Remove from oven and let rest for 15 minutes before serving with sour cream, diced tomatoes, and cilantro.