Prepare the Grill: Preheat your barbecue or indoor grill pan over a medium-high heat, aiming for around 200°C (400°F). Clean the grates well and lightly oil them with a paper towel dipped in vegetable oil to prevent sticking.

Season the Salmon: Pat the salmon fillets completely dry with paper towels. This step is crucial for getting crispy skin. Rub the olive oil all over the fillets, then season generously with sea salt and black pepper on both sides.

Grill Skin-Side Down: Place the salmon fillets skin-side down on the hot grill. Let them cook undisturbed for 5-7 minutes. The skin should be golden brown and crispy, and it should release easily from the grill. If it sticks, give it another minute before trying to lift it again.

Flip and Finish Cooking: Carefully flip the salmon using a fish spatula. Cook for another 2-4 minutes on the other side. The cooking time will depend on the thickness of your fillets. The salmon is done when it's opaque and flakes easily with a fork. According to the Food Standards Agency, fish should be cooked until it is steaming hot and cooked all the way through. An instant-read thermometer should register 63°C (145°F) in the thickest part.

Rest the Salmon: Transfer the cooked salmon to a plate and let it rest for 5 minutes while you make the sauce. This allows the juices to redistribute, ensuring a tender fillet.

Make the Lemon Butter Sauce: While the salmon rests, place a small saucepan over medium heat. Melt the butter until it starts to foam. Add the minced garlic and cook for about 30-60 seconds, until fragrant. Be careful not to let it burn. What works best for me is to constantly swirl the pan.

Finish the Sauce: Remove the pan from the heat and stir in the fresh lemon juice, lemon zest, and optional capers. Finally, stir in the chopped fresh parsley and a small pinch of salt.

Serve Immediately: Place a rested salmon fillet on each plate and pour the warm lemon butter sauce over the top. Serve straight away.