In a bowl, mix all the batter ingredients until the mixture reaches a consistency similar to tahini.
Heat a deep pot of oil until it reaches a boiling temperature.
Dry the fish pieces with paper towels, sprinkle them with a little coarse salt, coat them with flour, and dip them into the tempura batter. Place the fish into the hot oil and fry until golden brown. Remove the fish and place it on a cooling rack.