Preheat oven to 350. Lightly spray a 13" x 9" baking dish with nonstick cooking spray.
In a large skillet over medium heat, melt butter; add rice, salt and diced tomatoes w/ pepper/onion. Heat through and pour into bottom of prepared baking pan. Sprinkle 1 cup of the cheese over top.
In same skillet, over med-high heat, sautee onion in the oil until translucent. Add diced cooked chicken, enchilada sauce, black beans, pepper, salt, adobo, cumin and 1 tbsp cilantro. Stir and heat through. Pour over top of mixture already in the baking pan.
Sprinkle remaining 1 cup cheddar cheese over top. (then scatter optional sliced black olives over cheese, if using them). Sprinkle with 2 tsp cilantro.