Heat oven to 350F.
Place salmon fillet on a large piece of foil (on top of a baking sheet) and sprinkle with sea salt and pepper.
Place thin pieces of butter and lemon slices over the salmon.
Drizzle generously with balsamic vinegar.
Wrap salmon tightly in the foil, so the salmon can steam in the pouch.
Bake at 350F for 30 minutes for thawed fish and approximately 40 minutes for frozen fish.