# Clean the inner sides of the horse mackerels, wash them and drain the water over them.
# Grease a baking tray with 2 tbsp olive
oil. Place the half of the half circle shaped sliced onion
into the tray.
# Place the horse mackerels over the onion
layer. Place remaining onion
slices, circle shaped tomato
es and lemon
slices over the horse mackerels.
# Sprinkle salt all over. Pour the remaining 2 tbsp olive
oil all over.
# Cover the tray with aluminum foil.
# Place the tray into the oven which is preheated to 390 F. Cook it for about 35-40 minutes.