In a bowl, mix vinegar, lemon juice, 1/2 cup water, sugar, dried chilies, cardamom, garlic, mustard seed, peppercorns, fennel, and coriander.
Add salmon and combine with mixture. Cover and chill from 2 to no more than 5 hours.
Place white and red onions in a nonstick frying pan. Drain marinade from fish into pan and bring to a boil.
Place salmon on onions. Cover and simmer about 1 minute until fish is opaque but moist-looking in center. Place fish and onion mixture in a jar or bowl. Let cool, then cover and chill at least 2 hours or up to 5 days.