Add butter and blend until smooth. Season with salt and pepper. Transfer salsa to bowl. Mix in cheese, limejuice, oil and vinegar. Season with salt and pepper.
Arrange bread slices on baking sheets, spread with garlic butter, and broil until brown and crisp.
Drain the salsa and serve with the toasts. Put the fish in a bag and pour the marinade in. Let sit for 30 minutes. Fire up the grill to high. Oil the grate and cook the fish skin side down for 5 to 6 minutes, until the skin is nearly black.