The recipe Peel and roughly chop 50g of ginger, then put it into the bowl of a food processor. Peel 1 large beetroot and add to the ginger, then process to a coarse paste, pouring in 120ml of groundnut oil as you go. Season with a little black pepper. Cut a 500g piece of salmon in 2. Pour the dressing into a ziplock plastic bag, then add the fish and seal. Refrigerate for a couple of hours. Set the oven at 180C/gas mark 4. Remove the salmon, still coated with marinade, from the bag and place in a shallow, ovenproof dish. Season with a little salt. Cover lightly with kitchen foil, then bake in the preheated oven for 15 minutes. Remove the foil and continue to bake for a further 8 minutes. While the fish is cooking, trim and wash a handful of beetroot leaves, then put them in a saucepan, still wet, and cover tightly with a lid. Bring to the boil, turn the leaves once, cover again and cook for a minute or so longer, until bright and wilted. Remove the fish from the baking dish and serve with the beetroot leaves. Serves 2 I have tried other fish like this, but the oiliness of the salmon is perfect with the beetroot. You can leave the fish in its marinade for anything up to 3 or 4 hours before you use it, but longer may make it become woolly. Once cooked, the salmon can be eaten cold, too. I made some of mine into a sandwich with dark rye bread, watercress and thinly sliced cucumber. Don’t forget a gherkin or two. The Observer aims to publish recipes for fish rated as sustainable by the Marine Conservation Society’s Good Fish Guide