Preheat the oven to 450 °F. Line a baking sheet with aluminum foil as the skin will stick to the pan.
In a small skillet or saucepan, melt the butter. Add the shallot and cook on medium heat for about 3 minutes, until the shallot softens.
Add the garlic and the lemon zest, cook for another minute. Cool slightly. Squeeze in half of the lemon juice.
Place the fish on the prepared baking sheet and season with salt and pepper, to taste.
Spoon the butter sauce over the fish.
Sprinkle with half of the minced dill.
Roast in the oven for about 15 minutes. The best way to check for doneness is to use a fork to gently prick the fish, and if it flakes easily, it's ready.
Use two spatulas to take the fish off the baking sheet in one piece, or cut it into sections for serving.
Squeeze the other half of the lemon juice over the fish and garnish with a little more fresh dill.
Notes
Doneness Tip: Steelhead trout is done when it flakes easily with a fork and reaches an internal temperature of about 145°F. Be careful not to overcook, as trout dries out quickly.
Thickness Matters: Thicker fillets may need 2–3 extra minutes in the oven. Start checking at the 12–15 minute mark to avoid overcooking.
Substitute Option: Salmon can be used in place of steelhead trout. Expect a slightly firmer texture and adjust cook time as needed.
Butter Sauce Tip: Spoon the butter, garlic, and lemon mixture evenly over the fish so it bastes while baking for maximum flavor.
Fresh Herbs: Fresh dill gives the best flavor, but dried dill can be used in a pinch (use about one-third the amount).
Foil Lining: Lining the pan with foil makes cleanup easier and prevents sticking.
Serving Suggestion: This trout pairs well with rice, roasted vegetables, or a simple green salad for an easy weeknight dinner.