Heat 1 tablespoon of the oil in a frying pan over a medium heat. Add the onion and leek and
cook, stirring occasionally, for 4 minutes, or until slightly softened.
Meanwhile, place the remaining oil in a small bowl with the lemon juice and herbs and season
with salt and pepper. Stir together well. Rinse the fish under cold running water, then pat dry
with kitchen paper. Arrange the fish in a shallow oven proof dish.
Remove the frying pan from the heat and spread the onion and leek over the fish. Pour the oil
mixture over the top, making sure that everything is well coated. Roast in the centre of a
preheated oven, 200ºC / 400ºF / Gas Mark 6, for 10 minutes, or until the fish is cooked
Arrange the cooked spinach on serving plates. Remove the fish and vegetables and serve next to
the spinach, with the vegetables arranged on top of the fish. Garnish with lemon slices and serve