Tuna Melt Sandwich

In a bowl, mix tuna, mayonnaise, celery, onion, salt, and pepper.

Spread butter on one side of each bread slice.

Place two slices, butter-side down, on a skillet over medium heat.

Spoon tuna mixture evenly onto each slice.

Top with a slice of cheddar cheese and the remaining bread, butter-side up.

Grill until golden brown on both sides and cheese is melted, about 3–4 minutes per side.

Slice in half and serve warm.