Cut the red paprika into diagonal slices (7mm thick) and the zucchini into 1cm thick rounds. Thinly slice the garlic and remove its core. Chop the parsley.

Pat dry the horse mackerel fillets. Season with salt and pepper, then lightly coat with flour.

Heat butter in a pan over medium-low heat. Add the paprika and zucchini, cooking until browned and tender. Season with salt and pepper, then remove from the pan.

Wipe the pan clean. Add olive oil and garlic, heating over low heat until the garlic turns golden brown. Remove the garlic, then add the horse mackerel fillets skin-side down. Cook until both sides are browned, then remove from the pan.

Wipe the pan clean again. Add butter and ponzu soy sauce, heating over low heat for 30 seconds to 1 minute until slightly reduced. Turn off the heat and mix in the parsley to create the parsley ponzu sauce.