Combine jalapeño, tangerine zest and juice. Add pepper. Pour into a small ramekin or bowl. To open the oysters, hold each in a heavy dish towel with rounded side of shell down. Work the tip of an oyster knife into hinge near narrow end of shell; twist knife to pop open the shell. Slide knife along the inside of upper shell to sever the muscle, then pull off top shell and discard.

Loosen oyster from bottom shell by sliding the knife under oyster. Remove any bits of shell debris or sand. Spread some rock salt in a layer on a serving plate. Place oysters in their shells on plate and serve with salsa. Spoon salsa over oysters to eat.