How to Make It
Preheat the oven to 450°. In a large skillet, melt the butter. Add the onion and cook over moderate heat, stirring frequently, until softened, about 6 minutes. Add the bell peppers and cook until just softened, about 5 minutes. Add the mushrooms, garlic and wine and cook, stirring occasionally, until the mushrooms are tender and just beginning to brown, about 8 minutes. Stir in the parsley, season with salt and pepper and keep warm.
Heat a very large ovenproof skillet until hot. Add the olive oil and swirl the skillet to coat. Season the salmon fillets with salt and pepper and add them to the skillet, skin side down. Cook the salmon over high heat until the skin is crisp, 3 minutes. Turn the fillets, transfer to the oven and roast for 10 minutes, until just cooked through.
Spoon the mushrooms and peppers onto plates, top with the salmon, skin side up, and serve with the lemon wedges.