Pat the mackerel pieces dry with paper towels. Cut the leek into 3 cm long diagonal slices.
Combine the canned tomato (liquid and all), miso, grated ginger, sugar and soy sauce in a bowl, and mix together well to make the seasoning ingredient sauce.
Heat up a frying pan over medium heat, add the olive oil and spread it around, and then add the mackerel and pan fry on both sides.
When both sides are browned, arrange the fish in the pan skin side up. Add the leek and shake the pan.
When the leek slices have wilted, add the combined seasoning ingredients. Turn the heat down to low and cover with a lid.
Simmer for about 10 minutes until there's no liquid left in the pan, and it's done.
Story Behind this Recipe
I used a recipe by a manufacturer of canned tomatoes as a reference.
Combine the seasoning ingredients beforehand. Crush up the tomatoes with a spoon. The skin side of the mackerel may stick to the frying pan, so cook that side quickly. If there's still lots of pan liquid after simmering, take the lid off to let some of the moisture evaporate.