Add butter to a large pan or griddle over medium heat.
Swirl butter to coat the pan.
Add buns, sliced side facing down.
Toast buns about 1 minute or until golden brown. Remove from heat.
Video
Notes
On the Grill
Spread butter on the cut side of each bun. Place butter side down on the grill away from the flame. Let them toast until they get nice grill marks, about 1 minute - depending on the heat in your grill.
In the Oven
Just like for toasting on the grill, spread butter on the cut side of each bun. However, in the oven you'll want to have the butter side facing up. Place the buns on a baking sheet with butter facing up. Set your oven to broil and place the rack high. Using a broiler will toast the buttered side quickly so the rest of the bun won't get dry. Toast for about a minute, watching carefully so the bun doesn't burn.