Cod with Romesco Sauce, Hazelnuts, Lemon, and Parsley

Preheat oven to 350º. Toast hazelnuts on a rimmed baking sheet, tossing once, until golden brown and fragrant, 7–10 minutes; let cool. Smash hazelnuts in a mortar and pestle until very coarsely ground. (Alternatively, you can crush using the bottom of a mug or small saucepan.) Transfer to a small bowl. Stir in 2 Tbsp. oil and season with salt; set aside.

Place a rack in upper third of oven and heat broiler. Broil peppers and tomatoes, skin side up, on a rimmed baking sheet, turning peppers occasionally, until charred all around and flesh is soft, 12–15 minutes.

Slip off tomato skins; discard. Transfer peppers to a medium bowl and cover with plastic wrap so they can steam a bit (this extends the cooking and also makes the charred peels easier to remove). Peel peppers (flesh should feel slippery) and discard seeds; coarsely chop. Transfer peppers and tomatoes to a mortar and pestle and smash, covering the mortar slightly with your hands to prevent juices from splattering everywhere, until mixture achieves a saucy consistency. (You can also do this by pulsing in a food processor.)

Transfer romesco sauce to a clean medium bowl. Add garlic, vinegar, paprika, cayenne, and remaining ¼ cup oil; season with salt and let sit 15 minutes.

Preheat oven to 350°. Place fish a rimmed baking sheet and rub with with 2 Tbsp. oil; season with salt on both sides. Bake fish until cooked through and a paring knife can easily slip through flesh, 10–12 minutes. Top with zest while fish is hot.

Toss parsley, lemon juice, a drizzle of oil, and a pinch of salt in a small bowl. Spoon romesco onto plates, then spoon reserved oily hazelnuts over sauce. Arrange fish over, then top with parsley mixture.