Tuna Melt Panini

Instructions

1. Prepare the tuna mixture
   In a medium bowl, combine the drained tuna, mayonnaise, diced red onion, lemon juice, Dijon mustard, black pepper, and dried oregano. Mix thoroughly with a fork, breaking up any large chunks of tuna until the mixture is evenly combined and creamy.
2. Assemble the sandwiches
   Lay out the bread slices on a clean work surface. Divide the tuna mixture evenly among 4 slices of bread. Top each with tomato slices, arugula or spinach, and 2 slices of cheese. Place the remaining bread slices on top to form sandwiches.
3. Butter the sandwiches
   Spread the softened butter evenly on the outside of each sandwich, covering both the top and bottom slices of bread. This will help create a golden, crispy exterior when grilled.
4. Grill the panini
   Heat a panini press or large skillet over medium heat. If using a skillet, place the sandwiches in the pan and press down with a spatula or another heavy pan. Cook for 3-4 minutes per side until the bread is golden brown and crispy and the cheese has melted completely.
5. Serve hot
   Remove the panini from the heat and let cool for 1 minute. Cut each sandwich diagonally and serve immediately while the cheese is still melted and gooey.