- Preheat the oven to 220 °C (425 °F).
- In a skillet, gently sauté the onions and celery in the oil for about 10 minutes. Add the garlic and breadcrumbs. Set aside.
- Place the fish steaks, side by side, skin side down at the bottom of a baking dish.
- Drizzle with the vermouth. Scatter the butter and onion mixture over the fish. Season with salt and pepper. Bake in the middle of the oven for about 10 minutes. Serve with lemon wedges and garnish with fresh tarragon.