Classic Tuna Melt

Bahan-bahan (4 porsi)

• 2 5 oz . cans of tuna in water (drained, $1.76)
• 2 celery ribs (finely diced, 1 cup, 105g, $0.38)
• ½ small red onion (finely diced, 80g, ½ cup, $0.27)
• 2 dill pickle spears (small dice, 80g, ½ cup, $0.29)
• ⅓ cup mayonnaise ($0.30)
• ¼ tsp salt ($0.01)
• ¼ tsp pepper (freshly cracked, $0.04)
• 8 slices roti penghuni pertama ($1,42)
• 8 slices cheddar cheese ($1.49)
• 4 Tbsp butter (divided, $0.50)