01 -
Combine tuna, mayonnaise, Dijon mustard, garlic powder, onion powder, salt, and black pepper in a mixing bowl. Stir in diced jalapeño, shredded cheddar cheese, and green onions if using.
02 -
Butter one side of each bread slice. Place buttered side down on a skillet over medium heat. Sprinkle shredded cheddar cheese on one slice, then spread tuna salad evenly over the cheese. Top with the second slice of bread, buttered side up.
03 -
Cook sandwiches for 3-4 minutes per side, pressing gently with a spatula, until bread is golden brown and crispy and cheese is melted.
04 -
Remove sandwiches from heat and let rest for 1 minute before slicing and serving with preferred sides.