1. Preheat the oven to 400°F (200°C). Heat the oil in a flameproof roasting pan over medium heat. Add the bacon and scallions, and cook for 2 minutes, stirring frequently. Add the flounder, skin side down, baste with the oil, and season with pepper.

2. Bake for 15 minutes, basting once or twice. Transfer each fillet to a plate. Drain the bacon and scallions in a sieve.

3. Heat the butter in a small saucepan over medium heat about 2 minutes, until golden brown. Add the reserved bacon and scallions with the lemon juice, and stir in the parsley. Spoon over the fish and serve immediately.