Dry white wine and Gruyère cheese give this fish casserole a rich flavor that hides its virtue. Before baking, we top the dish with seasoned whole-wheat breadcrumbs, which add a wholesome, nutty flavor and dietary fiber. For variety, you can substitute almost any mild white fish.
- Preheat oven to 400°F.
- Heat 1 tablespoon oil in a large ovenproof skillet over medium-high heat. Add onions and cook, stirring often, until just starting to soften, 5 to 7 minutes. Add wine, increase heat to high and cook, stirring often, until the wine is slightly reduced, 2 to 4 minutes.
- Place cod on the onions and sprinkle with thyme, salt and pepper. Cover the pan tightly with foil; transfer to the oven and bake for 12 minutes.
- Toss bread with the remaining 1 tablespoon oil, paprika and garlic powder in a medium bowl. Spread the bread mixture over the fish and top with cheese. Bake, uncovered, until the fish is opaque in the center, about 10 minutes more.