Classic Tuna Melt | Lazy Cooking

Ingredients

• 3 (6-ounce) cans solid, water-packed tuna, drained
• 3/4 cup mayonnaise
• 1/4 cup cornichons (dilled gherkin pickles), finely chopped
• 3 tablespoons red onion, minced
• 2 tablespoons lemon juice
• 1 tablespoon fresh dill, minced
• 2 teaspoons whole-grain mustard
• 1/4 teaspoon kosher salt
• 1/4 teaspoon black pepper
• 8 slices rye or sourdough bread, cut 1/2-inch-thick
• 8 sandwich slices extra-sharp cheddar
• 4 tablespoons unsalted butter, softened, plus more, to taste