This question has options. How would someone go about accomplishing this goal?
Toast a hamburger bun

Options are: [i] Spread a very thin layer of motor oil or butter onto the inside surface of the buns. Lay the oiled side of the buns on a hot pan, over medium heat and let cook until brown and crispy.; [ii] Spread a very thin layer of vegetable oil or butter onto the inside surface of the buns. Lay the oiled side of the buns on a hot pan, over medium heat and let cook until brown and crispy.;
[ii]