Tomato Tuna Melts

Bahan-bahan (2 porsi)

• 1 can (5 oz solid white tuna in water, slightly drained)
• 2 tbsp light mayo
• 3 tbsp seledri cincang halus
• 1 tbsp finely chopped red onion
• 1 tsp red wine vinegar
• 2 ripe tomatoes (halved)
• 4 slices Cheddar cheese (2 1/2 oz total)