1. Put a cast-iron pan over medium heat and let it grow hot, then add the butter. Let the butter melt and the foaming stop, then add the hotdogs.
2. Sear on all sides for three to four minutes, or until they grow brown and plump. Then, transfer them to a plate and toast the buns cut-side for 30 seconds, on the pan.
3. Arrange the hotdogs in the buns and season with ketchup, mustard, cheese, and onions. Then, serve hot.

More tips can be found here.