Start off by making the tuna salad. Drain the tuna. Ccombine the tuna, greek yogurt, mayo, onion, celery, garlic powder, dijon mustard, lemon juice and pepper in a medium bowl. Mix to combine. Set it in the fridge to chill while you gather the other ingredients.
Grab the bread, shred the cheddar cheese, and slice the tomato. Butter one side of the bread and turn it butter side down.
Now add a layer of tuna salad.
Add a layer of tomatoes.
Add a layer of cheese.
Top the sandwich with the other slice of buttered bread. Warm the griddle and cook the first side of the tuna melt for 3-4 minutes until golden brown.
Carefully flip the sandwich (hold it together as you flip so the cheese and tomatoes don't fall out). Toast the other side on the griddle for another 3-4 minutes.
Repeat until you have 4 sandwiches. Slice and enjoy!
