In a bowl, mix together the ingredients for the aioli. Season with salt and pepper to taste.
Preheat the oven to 400℉ (204℃).
Lightly grease a baking sheet with nonstick spray. Season the salmon with salt and pepper. Then place onto the baking sheet. Bake to an internal temperature of 140°F (71°C). While the salmon is cooking, toast the buns.
Toast buns in the oven or toaster oven.
Once the salmon is cooked, set aside to rest for 3 to 5 minutes.
Spread aioli on the inside of both halves of the toasted buns. Layer with lettuce, tomato, salmon, and onion.
Enjoy the sandwich with chips, pickle, and apple cider.