Clean, wash, quarter and seed the tomato. Dice the flesh. Peel and finely dice the onion. Drain the tuna, chop with a fork
Mix lemon juice, salt and pepper. Fold in the oil. Fold in diced tomatoes, onion and tuna
Remove the seeds from the melon and cut out balls or dice the flesh
Spread the baguette with salad cream. Cover 4 slices with 1 slice of ham and 1/4 melon each. Cover 4 slices with tuna salad. Garnish everything with basil