Heat 1 tablespoon coconut oil in a skillet until it melts on medium heat. Add chicken and cook about 4-6 minutes per side until completely cooked through. Remove from skillet onto a plate lined with a paper towel.
Add the remaining coconut oil to the skillet. Cook on medium heat, and once melted, add in the diced onions. Cook about 3-5 minutes until translucent, remove from heat, and immediately add in spinach. Mix well until spinach wilts.
In a casserole dish, layer the chicken, then the onion spinach mixture, followed by the beans, salsa, cilantro, and lastly the cheese. Cover and bake for 15 minutes.