Pat the salmon fillet completely dry with a paper towel and season both sides evenly with sea salt and black pepper.
Heat the olive oil in a medium stainless steel or cast-iron skillet over medium-high heat until the oil is shimmering.
Carefully place the salmon skin-side down in the pan and sear for 4 to 5 minutes without moving it to ensure the skin becomes crispy.
Flip the salmon and cook for an additional 2 to 3 minutes until the flesh is golden and just cooked through, then remove the fish from the pan and set aside.
In the same skillet, reduce heat to medium and add the minced garlic, sautéing for 30 seconds until fragrant but not browned.
Add the fresh spinach to the skillet in batches, tossing frequently until all leaves are wilted.
Stir in the full-fat coconut milk, lemon juice, and ground nutmeg, simmering for 1 minute until the sauce thickens and coats the spinach.
Transfer the creamy spinach to a plate and top with the pan-seared salmon fillet to serve.