Prepare the salsa by combining all ingredients in a medium bowl; toss to combine and chill for at least 2 hours. Taste for seasonings and adjust accordingly.
FOR THE FISH
Preheat oven to 450F.
Wash fish fillets and pat dry with paper towel.
Brush each fillet with olive oil and season with salt and pepper.
Set a grill pan or a cast iron pan over medium-high heat.
Place the salmon, skin-side up on the pan; cook for 5 minutes, or until lightly browned.
Turn the salmon over, skin-side down, and transfer pan to the oven.
Continue cooking for 5 to 7 minutes, or until done. Salmon is done when it starts to release the white substance, or fat.
Remove from oven and let stand 2 minutes.
Transfer to a plate.
Spoon previously prepared salsa over fish.
Serve immediately.
Notes
If grilling the fish on a grill:1. Heat a grill to medium-high. 2. Season the salmon as directed in the recipe. 3. Brush the cooking grate with oil. 4. Place the salmon, skin-side-down, on the grill and cover. 5. Cook, undisturbed, until the salmon just starts to release its fat; about 10 to 15 minutes for most 1-inch-thick fillets. 6. Remove the fish from grill and transfer to a plate. 7. Spoon salsa over fish and serve.