Prepare the fish by spreading with a layer of pesto and then sprinkle the orange zest over the top. Season lightly and place in a steamer. I use a Japanese bamboo basket steamer but other types can be used.
In the bottom of a wok or other large saucepan place the water, tea bags and orange juice. Bring to the boil and then place the steamer inside and steam for 5 to 6 minutes, until the fish flakes easily with a fork.
Try other flavours of tea. I have tried Orange Pekoe and Assam but always come back to my favourite Lap Sang Suchong. I have also used alternative pestos such as sorrel or rocket pesto.