Step-by-Step Instructions

• Begin by draining the tuna and placing it into a medium bowl. Add the mayonnaise, Dijon mustard, finely chopped celery, diced red onion, and lemon juice. Season with salt and pepper to taste. Stir thoroughly until the mixture is creamy and all ingredients are well combined.
• On a clean surface, lay out the eight slices of whole-grain bread. Generously spread softened butter on one side of each slice.
• Place a large skillet or griddle over medium heat, allowing it to warm up.
• Once the skillet is heated, place four slices of the buttered bread into the skillet, buttered side down.
• On each slice of bread in the skillet, layer one slice of creamy cheddar cheese, followed by a generous scoop of your prepared tuna mixture, tomato slices, and arugula or spinach before topping with another slice of cheddar cheese.
• Take the remaining slices of bread and gently place them on top, buttered side up, forming your sandwiches.
• Grill the sandwiches for about 3–4 minutes per side, until the bread is golden brown and the cheese melts.
• Once toasted, remove from the skillet, let cool for a minute, and cut each sandwich in half before serving warm.