How to Make It
Preheat the oven to 400°. In a bowl, mix the peppers, jalapeño, olive oil, onion, lime juice and cilantro. Season with salt and pepper.
Butter a ceramic baking dish. Season the fish with salt and white pepper and arrange the fillets in the dish, skin side down. Scatter the 2 tablespoons of cubed butter around the fish and add 1/2 cup of water. Bake the fish for about 15 minutes, until just cooked.
Heat a cast-iron skillet. In a bowl, toss the tomatillos with the canola oil and season with salt and white pepper. Arrange the tomatillos in the skillet and cook over high heat, turning once, until charred, 2 minutes.
Transfer the fish to plates, top with the tomatillos and salsa and serve.