Mix milk, eggs and flour, season with salt. Leave to swell for 10 minutes. For the filling, drain the tuna and pluck into large pieces. Wash, clean and dice the tomatoes. Peel and halve the onion and cut into thin rings.
Wash parsley, dab dry, put something aside for garnishing. Chop the rest finely. Mix prepared ingredients with 2 tablespoons of oil, season with salt, pepper and sugar. Heat 1 tablespoon of oil in a pan (24 cm Ø). Add half of the dough, bake a golden brown pancake, keep warm. Heat the rest of the oil in the pan and bake another pancake from the remaining dough. Spread the tomato mixture on one half of each pancake. Sprinkle with cheese. Fold the pancakes once over the filling.
Add half of the dough, bake a golden brown pancake, keep warm. Heat the rest of the oil in the pan and bake another pancake from the remaining dough. Spread the tomato mixture on one half of each pancake. Sprinkle with cheese. Fold the pancakes once over the filling. Serve garnished with parsley