Pat the fish bone-dry. Surface moisture dilutes the seasoning and keeps the glaze from clinging. Thirty seconds with a paper towel makes a real difference.
Start the glaze while the oven preheats. By the time the oven hits 400°F, your glaze is reduced and cooling. That overlap is how this lands on the table in 35 minutes.
Watch the glaze, not the clock. Balsamic brands vary in thickness. Pull it when it coats a spoon and leaves a clear line when you swipe a finger through it. Over-reduce it, and it turns into hard candy when it cools.
Use a thermometer for perfect fish. Steelhead is thinner than most salmon and can overcook fast. Check at 9 minutes; the fish keeps cooking for a minute or two off the heat.
Want more color? Switch the oven to broil for the final 1 to 2 minutes to caramelize the glaze, and stay close, because sugar goes from bronzed to burnt in seconds.
Swap the fish: Salmon is a one-for-one swap; thicker center-cut pieces may need 12 to 15 minutes. Arctic char works beautifully too.
Swap the wine: No white wine? Use chicken broth, or an extra 1 tsp. lemon juice plus 2 tsp. water.
Swap the sweetener: Maple syrup can replace the honey for a slightly less floral glaze.
Swap the seasoning: Cajun seasoning or a pinch of smoked paprika plus cayenne can replace Creole seasoning. If yours is salty, cut the sea salt on the fish to 1/4 tsp.
Garlic shortcut: Jarred minced garlic is perfectly fine here, since it softens in the simmering glaze. No cast iron? Any oven-safe skillet or a parchment-lined baking dish works.
Finish it like a chef: Scatter fresh parsley or sliced green onions, add a pinch of red pepper flakes, or squeeze fresh lemon right before serving for freshness and contrast.