You can absolutely freeze the salmon after baking. Place it in an airtight freezer container or zip top bag and freeze for 4 to 6 months. However, the sauce doesn't freeze well. It separates and gets all gloppy. So, if you are going to freeze the fish for later, I suggest only making a 1/2 or 1/4 recipe of the dill sauce and make some fresh when you reheat the salmon.