In a medium bowl, combine the drained tuna with mayonnaise. Add the finely chopped celery if you’re using it, and season with salt and pepper to taste. Mix well until everything is nicely combined.

Take two slices of bread and spread a generous amount of the tuna mixture on each. Top with a handful of shredded cheddar cheese, then cover with the other two slices of bread.

In a frying pan, melt 1 tablespoon of butter over medium heat. When the butter is bubbly, carefully place the assembled sandwiches in the pan.

Cook the sandwiches for about 3-4 minutes on one side until they’re golden brown. Carefully flip them over, adding the remaining butter to the pan if necessary, and cook for another 3-4 minutes until the other side is also golden brown and the cheese has melted.

Once both sides are crispy and the cheese has melted, remove the sandwiches from the pan. Let them cool for a minute, slice in half, and serve immediately.