Grilled mackerel sandwich (Balık ekmek)

1. Fillet the mackerel (or buy fillets), pull out the pin bones with tweezers, season and brush with the olive oil.

2. Slice the red onion into thin half-moons and rub with the sumac and a pinch of salt; shred the lettuce.

3. Cook the fillets in a hot griddle pan skin side down for 3 minutes, then turn and cook for 1-2 minutes.

4. Split the bread pieces (about 20 cm lengths of loaf) lengthwise and toast the cut sides in the fat in the pan.

5. Fill each piece with lettuce, a mackerel fillet and sumac onions, and squeeze over some lemon.

6. Serve immediately, hot.

Tip: The iconic street food of the Golden Horn, cooked on boats and handed over to the quay. It's best with freshly caught mackerel – the fish should have bright eyes and firm flesh.