Tender, juicy, and delicious steelhead trout baked with lemon, butter, garlic, and fresh dill. An easy 30-minute fish dinner served with a creamy dill sauce.
Preheat the oven. Heat your oven to 400°F. Line a baking sheet with parchment paper or foil large enough to fold over the fish to seal.
Prepare the trout. Pat the fillet dry with paper towels and place it, skin side down, on the parchment or foil. Use tweezers to remove any remaining bones. Season the fish with salt and pepper.
Add flavorings. Drizzle the fillet with the melted butter and the olive oil. Sprinkle over the minced garlic and chopped dill. Arrange lemon slices over the top of the fish.
Seal the packet. If using parchment, fold the top over and crimp the edges tightly to form a sealed packet (“en papillote” style). If using foil, fold and crimp edges to seal, but avoid pressing too tightly against the fish.
Bake. Place the packet on the baking sheet and bake for 18–22 minutes, depending on the thickness of the fillet. The fish is done when its internal temperature registers at 145˚F, or it flakes easily with a fork and has turned opaque throughout.
Meanwhile, make the horseradish cream sauce. Whisk all the sauce ingredients in a bowl until smooth. Chill for 10–15 minutes, if possible, to let the flavors meld.
Let it rest. Remove the fish from the oven and carefully open the packet (watch for steam), transfer the fillet to a serving platter, and let it rest for 5 minutes. Spoon some of the buttery cooking juices over the top.
Serve. Garnish with extra dill, and serve it with the prepared creamy horseradish sauce and lemon wedges.