Combine mustard and 2 Tablespoons melted butter in a small bowl and mix well. Oil the bottom of a baking dish. Preheat an oven to 450 degrees F. Add salmon fillets, skin side down to the baking dish. Sprinkle salmon with salt. Spread the mustard mixture generously over salmon and season with pepper. Place salmon in oven and roast for 10 minutes. Mustard crust should bubble and begin to turn brown. If necessary place it under the broiler for 1-2 minutes to brown. Meanwhile, heat sauce. Spoon 2 Tablespoons of sauce over each fillet to serve.
We used a store bought Marionberry Chipotle Sauce, but any savory berry sauce will work. These sauces are readily available in most gourmet or natural food markets. Many of them are naturally gluten-free. The spicy sweet flavor is a perfect topping for the tartness of the mustard in this dish....Delicious!