Remove salmon fillets from refrigerator and pat thoroughly dry with paper towels. Season both sides with salt and pepper.
Preheat a large heavy skillet (preferably cast iron) over medium heat for 3 minutes until hot.
Add olive oil to the hot skillet and swirl to coat the surface.
Carefully place salmon fillets in the pan, skin-side down (if using skin-on). Press down gently with a spatula to ensure the skin makes full contact with the pan.
Cook undisturbed for 4-5 minutes until the skin is crispy and golden brown, and the salmon has cooked about 3/4 of the way up from the bottom.
Carefully flip the salmon and add butter to the pan. As butter melts, add minced garlic and capers.
Cook for another 2-3 minutes, occasionally tilting the pan and spooning the garlic-caper butter over the salmon.
Squeeze half a lemon over the salmon and continue cooking until the internal temperature reaches 125°F (52°C) for medium-rare or 145°F (63°C) for well-done.
Remove from heat and transfer to serving plates. Garnish with fresh herbs and lemon slices.