Preheat the oven to 400 degrees.
Line a rimmed baking sheet with aluminum foil and coat with cooking spray. Place the fish fillets on prepared baking sheet, and sprinkle with salt.
In the bottom of a small skillet over medium-high heat, heat the oil and saute the garlic for about 1 minute.
Add the cilantro, walnuts and lemon juice, stirring well to mix, and cook for 2 minutes, until heated through. Set aside to cool.
Bake the fish fillets for about 5 minutes, or until the fish flakes easily with a fork. Serve each fillet topped with a spoonful of the nut mixture.