In a medium saucepan, bring 1 quart of water to a boil. Add the capers and simmer over moderately high heat for 5 minutes. Drain the capers and pat dry with paper towels.
In a large skillet, heat 1/4 cup of the olive oil. Add the lemon zest and cook over moderately high heat, stirring, until starting to brown, about 40 seconds. With a slotted spoon, transfer the zest to paper towels to drain.
Dredge the capers in the flour and shake off any excess. Reheat the olive oil. Add the capers and fry over moderately high heat, stirring often, until crisp and browned, about 3 minutes. With a slotted spoon, transfer the capers to paper towels to drain. Wipe out the skillet.
Add the remaining 2 tablespoons of olive oil to the skillet and heat until shimmering. Season the halibut with salt and pepper, add it to the skillet and cook over high heat until browned and crisp on the bottom, about 4 minutes. Turn the fillets and cook over moderate heat until just white throughout, about 4 minutes longer. Transfer the fish to plates and tent with foil to keep warm.
Add the wine to the skillet and cook over moderately high heat until it is reduced by half, about 3 minutes. Add the lemon juice and remove from the heat. Swirl in the butter until melted and season the sauce with salt and pepper. Drizzle the sauce over the halibut, top with the fried lemon zest and capers and serve.
Notes: Variations: Serve the fried capers and lemon zest on pizza, grilled chicken, in salads or in an omelet.