The technique used here is similar to a cured salmon or gravlax. The longer you leave the fish in the salt mixture, the drier and saltier the end result. If you prefer the fish on the rare and juicier side, halve the curing time to overnight only.
1.1 lb / ½ kg skinless Spanish Mackerel fillet, cut into 1-inch / 2-cm thick slices
1 stalk thyme, leaves only
1 fresh red chili pepper, thinly sliced
Mix the salt and black pepper in a bowl. Roll the fish slices in the mixture and transfer to a colander placed over a bowl. Cover and refrigerate for 24 hours. Keep the remaining salt and pepper mixture.
After 12 hours, flip the fish over and add more of the salt and pepper mixture.
Remove the fish from the salt mixture, gently shake off any excess salt and quick-rinse under the tap (using as little water as possible) to wash off the salt.
Gently pat dry with a paper towel and slice as thinly as possible. Transfer to a serving plate, sprinkle the thyme leaves and chili slices and finish with a drizzle of olive oil. Serve with a thick slice of toasted challah.