Preheat oven to 350 degrees F. Put chiles onion, garlic, salt and water in a blender. Put meat in a casserole. Once sauce is done, add to meat. Poke meat several times with a knife. Cover with foil and place in oven.
Bake for 1 1/2 hours checking regularly until it is tender and inner temperature is 180 degrees F.
Add butter to a sauce pan in a medium heat. Once butter is melted, add rice stirring slowly for 2 minutes. Add chicken stock and cover. Let boil for 20 to 25 minutes checking regularly until rice is done.