Step 1

Place walnuts in a large skillet and heat over medium until nuts smell toasted and fragrant, shaking pan often to prevent burning, about 5 minutes. Transfer walnuts to a blender, and return pan to stove.

Step 2

Add 1 Tbsp. oil to the pan, along with shallots. Cook 2 to 3 minutes, until softened. Add garlic; cook 30 seconds, until aromatic. Stir in rosemary, 1/2 tsp. salt, and vinegar; cook 1 to 2 minutes, until harsh vinegar smell dissipates. Add broth and simmer 3 minutes. Stir in lemon zest, and carefully pour mixture into blender with walnuts. Blend on HIGH until smooth and creamy; set aside.

Step 3

Add remaining 2 Tbsp. oil to pan and increase heat to medium-high. Season salmon with remaining 1/2 tsp. salt and black pepper. Place salmon skin side down in pan; cook, undisturbed, pressing gently on fillets with a spatula to ensure skin is in full contact with pan, until skin is golden and crisp, about 5 minutes. Gently flip, turn off heat, and continue cooking until fish is opaque in the center, about 2 more minutes for medium-rare.

Step 4

Pour walnut sauce into skillet and add garnishes of choice (chopped walnuts, fresh herbs, lemon zest, etc.) Serve with grain and/or vegetable of choice.