First you have to clean the fish. Open the belly of the snapper with the scissors (1), starting from the anal orifice up to under the gills. Extract all the viscera (2) and the two gills (3), pulling them firmly.
Wash the fish, in particular in the gills (4) and in the belly (5) to remove all blood and viscera residues. Then leave the fish aside (6).
Peel the potatoes (7) and cut them into thin slices (8) of about 2 millimeters thick. Leave in a separate bowl (9).
Wash the tomato (10) and cut in circular slices (11) of a couple of millimeters thick. Leave in a separate bowl (12).
Peel the onion (13) and cut in circular slices (14). Leave aside (15) in a bowl.
Wash the lemon and cut in circular slices (16) which you will then cut in half (17). Leave aside on a saucer (18).
Peel the garlic cloves (19) and cut into small slices (20). Leave aside on a saucer (21).
Salt the belly of the fish (22) and stick in three slices of garlic (23) and one in the gills (24).
Stick a couple of slices of lemon (25) in the belly, and put one in the gills (26). Place also the parsley in the belly (27) of the fish.
Take a large baking pan and pour on the bottom some extra virgin olive oil (28). Stratify a lay of potato slices (29), and sprinkle with salt (30).
Then lay the fish on top of the potato bed (31) and place the tomato slices (32) on top of the fish. Add a little bit of salt on the tomatoes (33).
Then lay a few slices of onion (34) on top of the tomatoes, and pour a little olive oil on top (35). Sprinkle with freshly ground black pepper (36).
Bake (37) the pan in a preheated oven at 180°C for about half an hour. Once done, take out of the oven (38) to serve immediately on the table (39).