Preheat oven to 400. Rinse and pat dry the salmon, then place on a parchment-lined baking sheet and season with 1/2 teaspoon salt and pepper. Roast until cooked through, about 15 minutes. Allow to cool 5 minutes then using fork s flake or separate the salmon into small pieces.
Place salmon in a large bowl. Add onions, breadcrumbs, parsley, mayo, mustard, egg, & lemon juice. Season with 1 teaspoon salt and pepper, then mix gently.
Using a 1 1/2 inch scoop (or your hands), form the mixture into balls and place on a parchment-lined baking sheet.
If you are freezing the salmon cakes, leave them on the baking sheet and place them in the freezer. Once firm, store them in a resealable freezer bag until needed. (When you want to cook them, place them back on a baking sheet while still frozen, and allow them to thaw in the fridge for at least 4-5 hours. Then proceed with baking per the next step in these instructions.)
To finish the cakes, bake on 400 for about 15-20 minutes, just until they start to crisp and become golden.
For The Sriracha Lemon Aioli:
Combine all ingredients in a small mixing bowl, and whisk thoroughly. Adjust salt and pepper to taste.