- 2 bunches asparagus, trimmed, halved lengthwise if thick, divided
- 6 Tbsp. unsalted butter
- 7 Tbsp. extra-virgin olive oil, divided
- 1tsp. Aleppo-style pepper
- 2½lb. skinless halibut, salmon, or arctic char filletKosher salt, freshly ground pepper
- 2 bunches ramps or scallions, trimmed
- ¾cup Castelvetrano olives, pitted, torn
- ¼cup finely chopped chives
- ¼cup fresh lemon juice
- 2 Tbsp. coarsely chopped tarragon, plus leaves for servingBoiled small waxy potatoes and lemon wedges (for serving)
Preheat oven to 325°. Thinly slice one-quarter of asparagus into coins and place in a medium bowl; set aside.
Heat butter and 2 Tbsp. oil in a small saucepan over medium. As soon as butter is melted, add Aleppo-style pepper and remove from heat.
Season fish with salt and black pepper on both sides and place on a rimmed baking sheet. Scatter ramps and remaining asparagus around fish; season with salt and black pepper. Pour butter mixture over fish and vegetables. Give vegetables a toss to evenly coat. Roast, undisturbed, until fish is just opaque in the center and asparagus is bright green and tender, 15–25 minutes, depending on the thickness of your fillets.
Toss olives, chives, lemon juice, 2 Tbsp. tarragon, and remaining 5 Tbsp. oil with reserved asparagus; season with salt and black pepper.
Transfer fish to a platter; top with ramps and asparagus. Spoon some olive mixture over, then scatter tarragon leaves over. Serve with potatoes, lemon wedges, and remaining olive mixture alongside.