Preheat oven to 375°F. Line a large rimmed baking sheet with parchment paper.
Place walnuts in food processor; coarsely chop. Add Dijon mustard, maple syrup, garlic, lemon juice olive oil and dill; pulse until crumbly. Mixture should stick together.
Spoon 1/3 cup of walnut crumb mixture over each fillet; gently press the crumb mixture into the surface of the fish.
Bake until the fish flakes easily with a fork, about 20 minutes, depending on thickness.