Turn on the oven to 190°C air circulation and rack in the middle.
Prepare the filling by combining the tomato, onion, parsley, lemon zest and juice, capers, coriander and half of the salt and pepper. Keep aside.
Use a non-stick baking dish lightly oil it. Butterfly the sardines and odd them to the dish skin side down. Brush them with oil and season them with the remaining salt and pepper. Place in the oven and cook for 20’.
Remove from the oven and add half of the in a serving plate. Add on top some of the filling and place above a similar size sardine from the rest.
Serve and garnish with more parsley and drizzle with some olive oil.