Cut the fish into small slices. Salt, pepper, leave for 20 minutes. Cut the potatoes into circles. Put in the form. Salt and pepper. Put our fish in a second layer. Tomatoes, sliced in circles, are the third layer. The fourth layer is potatoes. Salt a little. Then grease with mayonnaise. Rub the cheese on a fine grater. We spread it with the last layer. Sent to the oven for 40 minutes.