Preparation Arrange a rack in top third of oven; preheat to 450°F. Line an 18x13" rimmed baking sheet with foil. Lay trout open like a book, skin side down and alternating head-to-tail next to each other on one half of pan. Sprinkle flesh with Old Bay, then dot with half of butter. Arrange lemon slices over. Drape a long (about 30") piece of foil crosswise over other half of pan. Toss together corn, green beans, tomato, salt, and remaining butter on foil. Fold edges up and over to create packet; pinch edges closed. Roast until trout is opaque and cooked through, about 10 minutes. You want to check the thickest part of the flesh—if you need to lift a lemon to look at it, do so, and continue roasting until it’s totally opaque. While fish is cooking, whisk mayonnaise, lemon juice, and pepper in a small bowl until smooth. Divide trout and succotash among plates. Serve with mayonnaise sauce alongside.
Preparation Arrange a rack in top third of oven; preheat to 450°F. Line an 18x13" rimmed baking sheet with foil. Lay trout open like a book, skin side down and alternating head-to-tail next to each other on one half of pan. Sprinkle flesh with Old Bay, then dot with half of butter. Arrange lemon slices over. Drape a long (about 30") piece of foil crosswise over other half of pan. Toss together corn, green beans, tomato, salt, and remaining butter on foil. Fold edges up and over to create packet; pinch edges closed. Roast until trout is opaque and cooked through, about 10 minutes. You want to check the thickest part of the flesh—if you need to lift a lemon to look at it, do so, and continue roasting until it’s totally opaque. While fish is cooking, whisk mayonnaise, lemon juice, and pepper in a small bowl until smooth. Divide trout and succotash among plates. Serve with mayonnaise sauce alongside.