- 1/2 cup blanched hazelnuts
- 1 garlic clove, chopped
- 1 cup (packed) fresh cilantro leaves with tender stems
- 1/2 cup (packed) fresh flat-leaf parsley leaves with tender stems
- 1 tablespoon capers
- 1 teaspoon finely grated lemon zest
- 1/2 cup olive oil
- Kosher salt
- 1 tablespoon vegetable oil
- 4 6-ounce pieces skin-on salmon fillets
- 2 tablespoons unsalted butter, cut into pieces
- 2 heads Little Gem or other small lettuce, leaves separated
- Preheat oven to 400°. Toast hazelnuts on a rimmed baking sheet, tossing occasionally, until golden brown, 6-8 minutes. Let cool.
- Pulse garlic, cilantro, parsley, capers, lemon zest, and 1/4 cup hazelnuts in a food processor until finely chopped. With machine running, gradually add olive oil; season relish with salt. Coarsely chop remaining hazelnuts.
- Heat vegetable oil in a large ovenproof skillet over medium-high heat. Season salmon with salt and cook, skin side down, until skin is crisp (do not disturb), about 4 minutes. Add butter and cook, basting constantly, 1 minute. Transfer to oven and roast salmon, basting once, until medium-rare (mostly opaque but still slightly translucent in the center), about 3 minutes.
- Serve salmon, skin side up, with lettuce, topped with relish and chopped hazelnuts.
- Do ahead: Relish can be made 6 hours ahead. Cover and chill.