Prep the halibut: Pat the halibut fillets dry with paper towels. Season both sides lightly with salt and seafood seasoning.
Sear the fish: Heat olive oil in a large skillet over medium-high heat. Add the halibut and sear for 3–4 minutes per side, until golden and just opaque in the center. Remove to a plate and keep warm.
Start the sauce: Reduce the heat to medium. Add 2 tablespoons of butter to the pan, then stir in the chopped shallots. Cook for about 1 minute, until fragrant.
Deglaze: Pour in the white wine and scrape up any browned bits from the bottom of the pan. Let it simmer for 1–2 minutes. About 2 tablespoons should remain of the wine in the pan.
Finish the sauce: Remove the pan from the heat and let it cool slightly. Whisk in 2 tablespoons of cold butter until the sauce looks silky. Stir in lemon juice, chopped dill, and heavy cream. Add salt and pepper to taste.
Serve: Drizzle the sauce over the halibut fillets and serve immediately.