Grilled Salmon with pita

1 tablespoon wasabi paste (see Notes) 2 teaspoons soy sauce 2 teaspoons rice vinegar 1/2 cup mayonnaise 1/2 pound salmon or arctic char fillet 2 teaspoons[...]

1 (1 pound) fresh or frozen skinless salmon fillet 1 small red onion, thinly sliced 1 tablespoon olive oil 1/4 teaspoon salt 1/4 teaspoon ground black pepper[...]