Heat the olive oil in a large skillet over medium heat. Add the diced onion and cook for 3 minutes until it softens. Stir in the minced garlic and cook for 30 seconds more.
Add the cooked rice and shredded rotisserie chicken to the skillet. Pour in the enchilada sauce, then sprinkle in the cumin and chili powder. Stir everything together until the rice and chicken are evenly coated.
Season with salt and pepper to taste. Let the mixture simmer for 4 to 5 minutes so the flavors combine and the sauce thickens slightly.
Sprinkle 1 cup of the cheddar cheese over the top and stir until it melts into the rice. Scatter the remaining 1/2 cup cheese across the surface, cover the skillet, and cook for 2 minutes until the cheese melts.
Remove from heat and serve with cilantro, green onions, and sour cream on the side.