Melt butter in a large skillet (cast iron works well for this purpose) on medium high heat. Add the chopped onions and sliced hot dogs. Cook, stirring occasionally, until the onions and the hot dogs are nicely browned, 5-10 minutes.
Add the sour cream and water, stir until creamy. Heat until steamy.
Top with parsley and serve over rice, noodles or on a sub.