• Heat the oven to 210 °C and line a baking sheet with baking paper.
• Always rinse the fish before cooking even though it was washed by the fish monger. Give it a rinse and gently dab it dry using clean kitchen towels. Place the fish on the tray lined with paper. Dab it dry one more time for extra measure.
• Use a sharp knife to score two or three lines or slits into the top of the fish in the skin. No need to over cut in depth and length, just enough to slide the lemon slices into them. Cut the lemon slices in half so they fit nice and snug.
• When you season the fish in the next step this includes the cavity of this fish. Season, a little spice and rub the olive oil inside and then fill the cavity with the lemon slices and a rosemary stalk each.
• Season the fish with the salt and pepper mix. Generously sprinkle the fish seasoning making sure to coat the fish. Drizzle olive oil over and gently rub or dab it into the spices. If you need to sprinkle a little more spice over do that and then bake. Don't over think it :)
• Bake for about 20 minutes and if you want the skin on top to crisp up, change the heat to grill and drop the rack down one level so it doesn't grill too fast. Watch it carefully when it's on grill, 5 minutes will be enough. How to tell the fish is ready? Use a fork, gently place it on the flesh of the fish where you made slits. Push the fork down to the spine, if the fish flakes and is tender it's ready. Or you can use a kitchen thermometer where the internal temperature will be around 54/55 °C.Remove the fish the from oven set it aside.
  

Sauce

• Add all the fish sauce ingredients into a pan starting with the butter and oil. Add the fish seasoning, garlic, fresh lemon juice, zest, white wine and bring to a simmer for 2 to 3 minutes. Taste and adjust accordingly and serve over the fish or on the side with fresh salad or greens.