Preheat broiler.
Combine tomatoes, oil, soy sauce, lemon juice and herbs. Cover and let stand 30-40 minutes.
Brush 4 salmon fillets with 2 T olive oil. Put fish on broiler pan with 8 1/8-inch thick slices of onion on top.
Broil 8 inches from heat for 12-15 minutes.
Remove. Spoon tomato salsa on top.