Tarragon Tuna Melt from Simply Recipes

Why I Love This Recipe
Recipe Credit: Original Recipe found on Simply Recipes
Ingredients You'll Need
1/3 cup mayonnaise
3 Tbsp chopped fresh flat-leaf parsley
1 thinly sliced green onion, including the greens
2 Tbsp chopped fresh tarragon leaves or 2 teaspoons dried tarragon, crumbled
Zest of one lemon
2 teaspoons lemon juice
1 teaspoon Dijon mustard
1/8 teaspoon freshly ground black pepper
2 6-ounce cans of solid white tuna, well drained and flaked
8 1/2-inch slices French or Italian loaf bread (or your favorite bread)
1 tomato, sliced thin into 8 slices
4 ounces sharp white cheddar cheese, grated (about 1 cup)
2 Tbsp butter, softened
Directions
In a medium sized bowl, mix the mayonnaise, parsley, green onion, tarragon, lemon zest, lemon juice, Dijon, and black pepper. Add the drained tuna. Mix with a fork to break up the flakes.
Lay out 4 slices of bread. Evenly divide the tuna mixture onto the slices. Top each with tomato slices and grated cheese. Spread one side of the remaining 4 bread slices with butter. Place bread slices, buttered side up, on top of the cheese.
Heat a large griddle, or couple cast iron skillets, on medium heat. Place sandwiches, buttered side down, onto the hot griddle. Gently butter the top bread slices. Cook for about 3 minutes, or until nicely browned on one side, and then use a metal spatula to lift up the sandwiches and carefully turn them to the other side. Cook for another 3 minutes or so, until the second side is browned.
Slice in half if you want. Serve immediately