How to Make It
In a food processor, combine the salmon with the lemon zest, 1 1/4 teaspoons of salt and 1/4 teaspoon of pepper. Pulse until the salmon is finely chopped but not pureed. Form the salmon mixture into four 3/4-inch-thick patties and refrigerate for 15 minutes.
Meanwhile, in a food processor, puree the mayonnaise with the scallion, anchovy, tarragon, parsley, dill, lemon juice and capers until smooth. Season with salt and pepper and scrape the dressing into a bowl. Refrigerate until ready to use.
Heat a grill pan or light a grill. Grill the salmon burgers over moderately high heat until cooked through, about 4 minutes per side. Transfer the salmon burgers to a plate. Grill the buns until toasted.
Spread the buns with the green goddess dressing and set a salmon burger on each bun. Top the burgers with the cucumber, tomato and avocado slices. Close the burgers and serve.