Put salmon in a long baking dish then season with sea salt and freshly cracked pepper, to taste.
Combine the maple syrup and mustard together in a bowl; mix well. Pour the marinade over the salmon, cover with plastic wrap and let it marinate in the refrigerator for 1-2 hours.
Preheat the oven to 400 degrees. Line a baking sheet with tin foil then coat with cooking spray.
Remove the salmon from the marinade and transfer it to the prepared baking sheet. Place into the oven and bake for 10-12 minutes, being careful not to overcook. Check the fish by gently poking through the fillet with a fork to see if it flakes apart.