The quality of this dish depends solely on the freshness of the sardines and the intensity of the grilling. Sardines are usually not cleaned (apart from rinsing) because their fat is crucial for flavour. They should be grilled over very hot charcoal so that the skin sears quickly and the inside remains juicy.
Traditionally, they are grilled in special wire baskets (grelhas) directly over the embers. If you do not have an outdoor grill, you can use a grill pan or an oven broiler, but the result will not be the same.
Rinse the sardines under cold water. Portuguese tradition does not require removing the heads or guts, as the internal fat adds flavor. Pat them thoroughly dry.
Season the sardines evenly and generously with coarse sea salt on all sides. The salt will help create a crisp crust and prevent sticking.
Heat the grill (ideally charcoal) to a very high temperature. The heat should be intense and stable.
If using a wire rack, lightly oil it or grill in special wire baskets.
Place the sardines on the grill. Grill for about 8-10 minutes per side (depending on the size of the sardines).
Do not turn them prematurely. Let them grill until the skin is seared and starts to separate easily from the rack.
The sardines are done when the skin is crispy and slightly charred, and the meat inside is opaque and juicy.
Remove the sardines from the grill and serve them immediately, usually placed on a thick slice of baked bread (pão saloio). The bread will soak up the fat that runs out during eating, which is considered a delicacy.
Serve with potatoes boiled in their skins and a simple salad (fresh peppers, tomatoes, onion) and drizzle with extra virgin olive oil.