Preheat outdoor grill to 475 degrees F.
While grill is heating, slice 2 limes into ¼-inch rounds. You will need about 3 slices per haddock portion.
In a small cast iron pot, add butter (or ghee), juice of 2 limes, garlic clove, capers and a pinch of red pepper flakes. Use salt and pepper grinders to add in about 1 teaspoon Himalayan pink salt and ½ teaspoon cracked black pepper.
Once grill is heated, add cast iron pot to the grates to melt the butter and bring sauce to a simmer.
Add lime slices directly to the grill grate, creating a bed for the haddock. Place the haddock skin-side down onto the lime slices, brush the tops with Caper & Lime Butter and season generously with more Himalayan pink salt and cracked black pepper.
Close the grill lid and let cook for 10 minutes, undisturbed, until fish reaches an internal temperature of 145 degrees F. Use a spatula to carefully remove the fish.
Spoon Caper & Lime Butter onto each filet and serve.