Set a cast iron Dutch oven over hot coals. Heat butter until melted. Add onion; cook, stirring often, until soft and deeply browned in parts, 5 to 7 minutes.
Pour salsa and chicken stock into the Dutch oven; bring to a boil. Layer in 1/2 of the chips, Cheddar cheese, and pulled pork. Repeat with the remaining chips, Cheddar cheese, and pulled pork (see Cook's Note for recipe link). Cover and cook until cheese is melted, about 5 minutes.
