Rinse the fish (inside and out) with cold water, pat dry, and make several diagonal incisions on both sides (approx. 5 mm deep). Season the fish inside and out. Stuff the abdominal cavities with the lemon slices, dill and garlic. Cover the fish and set aside. Preheat the oven to 60°C. Warm the platter and plates.
Place the Swiss chard in a wide-bottomed pan, pour in the water, season the vegetables, bring to the boil. Place the fish on the vegetables, reduce the heat, cover and cook for approx. 15 mins. Remove the fish and keep warm on the warmed platter. Add the cream and saffron to the Swiss chard, mix and bring to the boil. Reduce the heat, simmer for approx. 2 mins. until cooked.