Wash, clean, seed and cut the tomatoes into pieces. Wash and clean the fennel and cut into fine strips. Put both in a bowl and sprinkle with lemon juice
Peel the cucumber and cut off the ends. Remove the seeds and dice the cucumber. Peel and chop garlic. Wash coriander, shake dry, pluck off leaves and cut into strips. Put everything into the bowl. Season with salt and pepper and add oil. Mix everything
Drain the tuna and pluck into large pieces. Spread on the salad just before serving