Apply a non-stick spray to a 9x9-inch baking dish.
In a cup, mix the mustard, soy sauce, maple syrup and water.
Arrange the salmon in the pan and pour the maple sauce over the filets.
Cover the filets with thin slices of butter.
Sprinkle salt and pepper over the filets.
Distribute the nuts in the pan around the fish so that they will bake in the liquid.
Bake uncovered for about 15 minutes for average thickness filets. For thicker filets, add about 3-5 minutes; thiner pieces, bake about 3-5 minutes less.
Notes
To check salmon for ideal doneness, cut into the thickest part of the filet. Ideal doneness is when the flesh in the centre has turned pink and the salmon is still flaky and moist and tender in the centre.