Combine salmon, onions, water, and salt in a Dutch oven.
Bring to a boil and simmer 25 minutes.
Carefully transfer salmon to a platter.
Add lemon juice, vinegar, pickling spice, bay leaf and peppercorns to the fish stock.
Bring to a boil and cook 2 minutes.
Pour over fish and chill 24 hours before serving.
Drain and serve cold.