Preheat oven to 425 °F (218 °C). Set aside a 9x13" oven-safe casserole dish and lightly spray it with cooking spray.
In a large pot or skillet over medium-high heat, add cooking oil and once heated, add the onions. Cook until tender.
1 medium onion
Pour in the box of rice and vermicelli, including the seasoning packet.
6.9 ounce box of chicken flavored rice & vermicelli
Stir for two minutes then pour in the chicken broth and water.
2 cups chicken broth, 1 3/4 cups water
Bring to a boil then bring down to a simmer and cover for 20 minutes.
After the rice mixture has cooked for 20 minutes (note: not all the liquid will have cooked away, it finishes in the oven), add in the chicken. It's okay it doesn't cook all the way through as it finishes up in the oven.
2 large boneless, skinless chicken breasts
Remove from heat and add diced tomatoes, green chiles, cumin, chili powder, cayenne, salt, and pepper. Stir together.
15 ounce can of fire-roasted diced tomatoes, 4 ½ ounce can of chopped green chiles, 1 teaspoon ground cumin, 2 teaspoons chili powder, 1/4 teaspoon cayenne pepper, Salt and pepper
CAREFULLY pour mixture into prepared casserole dish.
Bake for 25 minutes, covered, then uncover the casserole and sprinkle cheese on top and let it melt.
Mexican blend shredded cheese
After removing from oven, let sit for 10-15 minutes. The waiting time is crucial because the liquid will continue to absorb into the rice and the casserole will have a thicker consistency.