Flatten hot dog buns with a rolling pin. In a small bowl, stir together butter, garlic powder, and onion powder. Spread all over outsides of buns.
In a large skillet over medium heat, sear hot dogs (working in batches if necessary) until charred, 2 minutes per side. Set aside.
Place a bun buttered-side down in skillet and top with 1/2 cup of cheddar cheese, a hot dog, a little more cheddar cheese, and 1/4 of green onions.
Cover and cook over medium heat until cheese melts, then use a spatula to close the bun. Repeat with remaining ingredients to make 4 cheese dogs total.