Peel the onion. Grate the cheese on a fine grater. Preheat the oven to 180°C.
Place the cod steaks on a baking sheet, salt and pepper to taste on both sides.
Cut the onion into half rings and the tomato into rings. Place tomato slices on top of the steaks. Mix sour cream and mayonnaise in a bowl. Lubricate the fish and tomatoes with the resulting mixture. Next add the onion. Sprinkle cheese on top.
Place the dish in the oven for 15-20 minutes.
Before serving, place lettuce leaves on a plate and cut 3-4 cherry tomatoes in half. Place the steaks on lettuce leaves, decorate with cherry slices and lightly sprinkle finely chopped dill on top.