How to Make It
Preheat the oven to 500°. Set 1 salmon fillet, skin side down, on a work surface and season with white pepper. Arrange the orange zest on the salmon and top with half of the fennel tops. Cover with the second salmon fillet, skin side up. Pack the remaining fennel tops on the sides of the salmon so that there's no exposed flesh. Tie the fillets together with kitchen string.
Spread the kosher salt in a large roasting pan in an even layer and bake for 15 minutes. Carefully spread 1 cup of the hot salt in the bottom of a large loaf pan that is at least 5 inches wide. Set the salmon in the pan and pour the remaining salt over and around the fish. Gently pack the salt and bake the salmon for 45 minutes.
Meanwhile, in a shallow bowl, combine the orange and lemon juices with the olive oil. Season lightly with table salt and white pepper. Add the sliced fennel and the capers, toss and let stand at room temperature for 30 minutes.
Scrape the salt off the top of the salmon. Using the string, gently lift the salmon from the pan and set it on a work surface. Scrape the salt from the sides and remove the string. Using a spatula, lift the top fillet and transfer it to a plate, skin side down. Discard the fennel tops and orange zest and cut each fish fillet in half. Lift the salmon from the skin, leaving behind the salt, and transfer to plates. Spoon the fennel salad on top and serve.