Marmitako | Basque Tuna and Potato Stew

Cut away and discard the dark bloodline in the tuna; it has a fishy, metallic taste. Cut the remaining flesh into 3 cm cubes, rub them with half the salt, and refrigerate. Keep the cubes the same size so they cook at the same time.

Heat the olive oil in a pot. Add the onion, both bell peppers, and the remaining salt. Cook over low heat for 10 minutes until softened but not browned. Add the garlic and stir for 1 minute. This slow cooking builds the stew’s sweetness, so do not rush it by turning up the heat.

Add the grated tomato and ñora paste and cook until the liquid evaporates, the mixture thickens, and the oil rises to the surface. Add the red pepper flakes at this stage. If you add the liquid before the oil separates, the stew will taste of raw pepper.

Do not cut the potatoes: insert the tip of a knife about 2 cm and lift to break off a piece, leaving each piece cracked and rough on one side. Add the potatoes to the pot and pour in the fish stock and apple cider vinegar. Cook over low heat. The stew will thicken on its own; when you draw a spoon through the middle, the path should stay open briefly.

Turn off the heat completely. Arrange the tuna cubes in a single layer on the surface of the stew and gently press them down with a spoon. Cover the pot and let stand for 6 minutes; the outside of the fish will become opaque pink while the center remains slightly translucent, and the flesh will begin to flake when touched with a fork. Spoon into bowls and serve hot.