tuna and cheese!
drain the tuna and mix it with 2-3 tablespoons mayo
add the chopped green onion and any other veggies you want
mix in most of the shredded cheese but keep some of it aside
split the hamburger bun in half and spoon the tuna mixture onto each of the buns then sprinkle the remaining cheese on top of each
put them on a baking sheet and broil them in the oven for about 5 mins