• Rinse and pat the fish dry. Thinly slice the lemon. Season the inside of the fish with a pinch of sea salt. Stuff the cavity with lemon slices and sprigs of fresh dill and tarragon. Repeat with the second fish, if using.
• Preheat the oven to 400℉. In a large bowl, combine the salt and water. Mix together with your hands until the salt feels like wet sand. The salt should be wet enough to hold together when squeezed, if not, add a bit more water.
• Spread a layer of the salt, a little wider than the fish, on the baking sheet. Place the fish on top of the salt. Pack the remaining salt around the fish, completely encasing it. Ensure that there aren't any holes in the salt.
• Bake the fish for 20 to 25 minutes until it reaches an internal temperature of 145℉. Use an instant read thermometer to stab through the salt crust and check the temperature of the fish. A larger fish will take longer.

Mustard Tarragon Sauce

• While the fish is baking, make the sauce. In a small mixing bowl, combine the Dijon mustard, grainy mustard, honey, lemon juice, apple cider vinegar, kosher salt and pepper. Whisk together until smooth. Add the olive oil, fresh dill and tarragon and whisk together. Chill until serving.

To Serve

• To serve the fish, crack the salt crust open and break it off the fish. Scrape off all the salt from the fish. Use a knife to gently peel back the skin. Using a large spoon, to separate the two sides of the top fillet, then slide the spoon under each side of the fillet and gently lift it off the hones. Transfer the fillet to a serving platter. Repeat with the other side of the top fillet.
• Sever the spine from the head and then peel it off the bottom half of the fish. To remove the bottom fillet, remove the fish and place upside-down on a cutting board. Peel the skin off and transfer the fillet to the serving platter. Serve the fish with the mustard tarragon sauce and enjoy!