Remove the skin and tendons from the liver and cut into sticks. Pour the flour onto a plate and roll the liver pieces in it. Shake off the excess flour.
Heat the oil in a frying pan and gradually fry the liver until crispy brown all over, lifting it out of the pan with a slotted spoon.
Transfer to a platter and sprinkle with salt, pepper and a little cayenne pepper on the spot.
Remove the skins from the onions, cut into narrow rings, place in a large enough bowl and sprinkle with a tiny bit of salt. Lightly knead the onion rings and rinse under running water. Shake off the water thoroughly.
Rinse the parsley, shake dry, chop finely, mix with the onions, a tiny bit of salt and the sumac. Rinse the tomatoes, dab dry and cut into eighths.
Serve the liver lukewarm with the onion salad, tomato quarters and parsley.
Rating by the author: succeeds easily