Place walnuts in food processor; coarsely chop. Add coconut flakes, lemon rind, olive oil and dill; pulse until crumbly. Mixture should stick together.

Arrange salmon fillets skin side down on parchment paper-lined baking sheets.

Brush tops with mustard.

Spoon 1/3 cup of walnut flake mixture over each fillet; gently press the flake mixture into the surface of the fish. Cover with plastic wrap; refrigerate for up to 2 hours.

Bake at 350 degrees 15 to 20 minutes, or until salmon flakes with a fork. Just before serving, sprinkle each with 1 teaspoon lemon juice.