Rub the salmon with a bit of olive or avocado oil and sprinkle some salt and pepper.
Bake the salmon low on 275℉ for about 40 minutes until just cooked through. Baking it low instead of a classic bake or broil kind of mimics the steamed effect and leaves the salmon super moist and not dried out when eaten cold the next day.
Place the salmon in the fridge until fully cooled. Slice the onions on a mandolin or as thin as you can get them. Loosely chop up the dill and lay both scattered all over the salmon. Generously drizzle balsamic vinegar over the entire salmon. Let it ‘marinate’ for at least 3-4 hours before serving. Take it out about an hour before serving and enjoy cold!
Notes
For a smaller crowd or more economical version, if your supermarket or fish store sells salmon tails, the dill and onions cover up the fish and still makes for a beautiful and delicious presentation.You can add the onions and dill up to a day before, but leave the balsamic for the day you're serving, so the dill retains its fresh crispy bite and doesn’t get too soggy from the balsamic.