1. Wash salmon and pat dry. Place in a glass dish, sprinkle with salt and pepper, and bake at 240 degrees Fahrenheit (120 degrees Celsius) for 20-30 minutes. It should look almost raw.
2. Remove fish from oven. Arrange onion slices on fish.
3. Blend together oil, vinegar, salt, and dill in a food processor or with a hand blender. Pour over fish. Cover with Gefen Parchment Paper and then tightly with aluminum foil. Marinate in the fridge for at least three days.
4. Serve cold, with fruit salsa on the side.