Preheat your oven to 425 degrees.
Make your tuna salad if you haven't already (I use lots of pickles, just a little mayo and onion.)
Butter one side of each slice of bread.
Put 1 slice of bread butter side down on a cookie sheet.
Put the tuna salad on top of the bread.
Top the tuna salad with cheese.
Top the sandwich with the other slice of bread, butter side up.
Bake for 8 minutes, then flip.
Bake for 4-6 more minutes.
Keep an eye on it to make sure it doesn’t get too done. Ovens will vary!