Step 1

Prepare a grill for medium heat. (Or preheat an oven to 375°F.) Tear 4 sheets of heavy-duty foil to measure about 16x12". Set 2 sheets on a work surface; top each with a remaining sheet of foil (you are making 2 double-layer packets). Divide tomatoes, garlic, rosemary, and nduja between sheets, placing in the center. Season halibut generously with salt and pepper and set on top. Drizzle with wine and oil. Bring opposite sides of foil together in the center; crimp tightly, pressing out air, to close.

Step 2

Place foil packets directly on grill grates (or a rimmed baking sheet if using oven) and cook until tomatoes are beginning to burst and halibut is opaque all the way through, 14–16 minutes. Let rest at room temperature a few minutes, then carefully open and transfer fish to a platter. Top with tomatoes and cooking juices from packets.

Step 3

Packets can be assembled 1 day ahead. Chill.