Line a broiler tray with aluminum foil, and lightly brush with olive oil. Place the black cod portions on the tray, skin-side down. Brush the fish with olive oil, and add salt and pepper to taste. Broil 4-inches from the heat source until nicely browned, about 10 minutes.
In a saucepan, lightly sauté the shallots and bell peppers in 2 Tablespoons of olive oil until soft, about 4 minutes.
Add the wine and tarragon and let simmer for about 10 minutes.
Add the cold butter, a little at a time, whisking until the mixture becomes creamy. Season with salt and pepper and set aside.
Plate the cod and pour the sauce over the fish.
